Gt grade carbon 105 or Merida ride disc 5000 or?

Goldenstar. Another vote for the GT. I got my carbon 105 late last year and as another comment stated, if I had to have one bike, this would be it. It's brilliant, and unless you're really going for it speed wise, you won't see a great difference. Compared with my Felt F4 (which I'm also very fond of) which is a light, stiff race bike, even more so with upgraded Mavic Kysrium S wheels, I only get 1.5km/h more on this. What I get on the GT is an all day capable bike and one that happily smashes along canal towpaths and light bridleways, even on stock road Contis. I'm planning to ride the North Coast 500 soon, and this should be a perfect bike for a few 100+ mile days. It's worth noting that some batches of the Stans wheels appear to have been made by a disgruntled robot on the Friday afternoon shift, as mine failed on two occasions. I've upgraded to Pro-Lites (courtesy of a good dealer and a warranty claim) and the bike's even better now. I've just got some gravel Challenge tyres to pop on for the summer, and as long as they fit,it should add even more to the bike. 

Please post your thoughts on the Spesh - a bunch of readers will be interested. 

Right, I'm in trouble. I can hear screeching kids and a frazzled wife. I need to sort the post bathtime apocalyptic scene upstairs.. 

So it does depend on what you actually want to use the bike for, and if you are prepared to swap tyres according to the surface you're riding on that day.  If you want to hang out with faster roadies, as others have said, the GT or Diverge would slow you down a bit, being heavier and less aerodynamic than an equivalently-priced out-and-out road bike. 

OTOH, with a disc-braked road bike, there may not be the tyre clearance to get cyclocross tyres on, plus the rims may not be wide enough to take them. UK off-road cycle paths are pretty variable, and using road tyres <28mm you might struggle; the more extreme the conditions, the more width and tread you want. I've ridden a couple of paths with guys on road bikes running 23/25mm tyres, and they get a lot of punctures. So you might want to check the clearances so you know what your options are.

Had you considered trading down say £250 and using the savings to buy a second set of wheels?

Or save £500+ and get the Merida Cyclo-Cross 500, and get the shop to stick Shimano hydraulics onto it. Bike is £1000, and getting them to switch the brakes shouldn't cost you more than £300 ish (as they can sell on the stock 105 levers). You could even throw a bit more money at it and get some really light wheels (some American Classic or Hunt) and you will still have some money left over, and in my view have a better bike.

The Carbon Merida Cyclocross 5000 is very nice, but it's a major price hike for a ride that isn't any better than the alu version (the 500 - although they share the same carbon fork) when doing the kind of riding you are talking about.

I have a Cyclo-Cross 500 and a Ride Carbon - both running shimano  RS685 hydraulic brakes, the ride on ultegra with very light semi areo wheels and GP4000 tyres and the cx is on 105 with stock hubs and stans Crest rims and CycloCross Speed tyres. The CX 500 is definately slower off the mark, and doesn't roll quite as well (1-2mph slower, depending on wind direction), but comfort on both is very similar on tarmac. I've had both off-road and although the Ride Carbon is excellent on gravel, and so OK for the odd shortcut, if I'm going to be on rough farm tracks or mtb routes, the Cyclo-cross is the one I'm on.

You could add the Merida Cyclo Cross 500 to your list of options. Similar spec to my Giant TCX SLR 2 but priced much better.

That is, if you're okay with aluminum bikes. I'm pretty sure there's a carbon Cyclo Cross option in the Merida range; you might want to check that out.

Much as I love my Grade 105 (size 55) I'm thinking of selling it as its not quite road focused enough for me. It's a just over a year old, let me know if you'd like to save some money over a new bike!

Had my Grade carbon 105 for nearly 18 months now and have been really pleased with it. Stock tyres absolutely rubbish, changing to Scwalbe Mondial have made it perfect for my regular rides in the new forest. Just back from a 5 hour ride, gears have never missed a change and the brakes are fantastic. Highly recommend.

There are a few people around at the mo considering a Grade. I have one. I say go for it. Its the best thing I ever bought.