How fit do I have to be to do a sportive?

I would not really bother with gels. For a 100k sportive a plate of pasta and a little sauce about three hours before hand will give your system a boost and maybe one sandwich along the way in tin foil not cling film (assuming your riding whilst eating) and cut it into squares. As for drinks, Orange squash diluted to taste, pinch of salt and add some honey(body builders use it to spike their energy before an event). It is just as effective as all those energy gels and much easier on the stomach. Just make sure you try whatever combo you like in advance and not on the day of the event.

First up. Enjoy yourself find your pace and stick at it. Don't be intimidated by others who treat it as a race. Latch onto groups and if they drop you wait till the next lot. If you are keeping pace with them do your turn at the front. If you feel the need to stop between feed stations to stretch or whatever do so.

Fuel up at the FS and blag a few gels/bars for between things. As for nutrition well there's plenty of thoughts. Before you start the sportive have a bowl of porridge and fruit or a pasta dish of some description a couple of hours before hand. Have a flapjack or something similar half an hour before you roll out. Also good to get some liquid in you as well at that point. Gel wise. It would be good to experiment before so you know what your system can handle. My preference is mule bars or high5 when using gels. Though some hand made flapjacks/fruit cake is hard to beat. Jelly babies are also a nice boost

Enjoy your time out and let us know how the sportive goes.

John the Monkey's dad here! He trundled around with his brother in law last year and this year he'll have me.

I'll be 65 by the time of the event,started cycling this spring and am coming up to 1,000 miles total since then - hardly a well honed athlete

My longest ride is about 40 miles but that seemed so comfortable that I've no worries about the 60 miler, except if some hills appear. The Cheshire Cycleway is very flat and the steepest ascent I can find is Artists Lane at Alderley Edge.

It isn't a race, so get off at the feeding points, have a stretch and enjoy a free slice of Soreen.

Don't worry about being too slow, somewhere behind you there will be an OAP trying to keep with a Monkey

I've done the challenge ride for the last two years (although it was 80km rather than 98km then).

IME, there's a range of riders that do it - I rode with my brother in law (who'd done 25 miles as his longest ride beforehand) at a 14mph average, and we were by no means the last ones in. The feed stops have been well stocked, and there's usually bananas on offer if you're unsure of the energy bars and gels. You'll be able to fill bottles at them all too, iirc, each one had fresh water & energy drink on offer. Feeds this year look to be at 25km and 60km (according to the ride manual).

If you're in Nantwich, you can do some decent rides on the Cheshire Cycleway to get a feel for the distance on similar terrain - I usually ride it from Crewe and it's pretty easy to get 60 or 70 miles - the route is well signposted, so route finding tends not to be a problem.

My own nutrition "strategy" revolves around the consumption of jelly babies, co-op wine gums, or Percy Pigs. Generally I have one every so often if I'm riding for more than an hour - if I'm out over 3 hours, I'll eat a flapjack, or something similar around the 1 1/2 / two hour mark.

I do not want to confuse you, but, have a look at 'optimal nutrition 4 sport' this site suggests that not eating too much is not necessarily a bad thing. I am trying these ideas at the moment. Also, you are more likely to over-hydrate than under-hydrate. But as I always say (but not always do) 'nothing new on race day'! Try different ideas and find what works for you. I train and race without eating or drinking much and would not like to think it does me or my results harm; if you are not hungry or thirsty then it is not necessarily a problem.

If you're doing 100km then you'll need to learn to eat on the bike. It takes a bit of time to find out what suits you - but essentially you want stuff with high carb content that's easily digestible.
Have a look on bikeradar.com for nutrition tips, maybe? For me, I tend to take a couple of energy bars, a couple of gels, and a packet of jelly or haribo. And one bottle with water, one with glucose/fructose/salt mix in it. I don't eat or drink all of that, but it's worth having more than you might need.
Obviously, the fitter you are, the less you need to eat. But for anyone, if you're riding more than about an hour, it's essential to drink and eat, little and often. Hydration is the most important, but to avoid the dreaded bonk you need to keep your sugar levels topped up.

I would echo what SideBurn has said. Ride within yourself, keep nibbling and drinking (and several short stops if you feel like it) and you'll be fine. You don't have to be epecially strong to get round a course like that. If you can hook up with a group riding at a sensible pace you'll not be riding into the wind all day.

Get some lumpy 30-50 mile rides in over the next couple of weeks, push the pace a bit if you're feeling up to it, and you'll surely have enough strength and stamina. Hope you enjoy yourself.

I generally work on an 80% rule. If you can ride 80% of the distance then you will be fine. But it is not so much the distance, it is the pace that could be a problem. Meaning that you need to set a reasonable pace for you and not be drawn into mini races. The route does not seem too hilly; just enter and take it easy(ish). What is the worst that can happen?