Gran Fondo Training Plan

Do all the above but also track your food and calorie intake.  Not obssessively but something like MyFitnessPal will make it easy to understand how much you are eating compared to the exercise that you are doing and will make it easy to lose some weight through the winter.

To find a plan type 'sportive training plan' into google:

https://www.google.co.uk/search?q=bikeradar+sportive+training+plan

Lots of sensible advice in GCN's videos - https://www.youtube.com/user/globalcyclingnetwork/playlists

Use the KISS principle but vary your rides, gradually increasing distance, speed or amount of climbing as weather etc allows.

You could include a 2x20 - and when you're fitter 3x20 - of moderate (tempo) efforts during a steady 2 hour ride, nothing too extreme and certainly not hard efforts. If there are no flat roads then find a route with gentler climbs and spin up them. Another time do big gear intervals, a few sets of 5mins with 5mins easy between during a ride.

For nutrition I would:

• reduce junk food, sugary foods and snacks, including sports nutrition products.
• eat more unprocessed food, especially vegetables.
• do a morning ride having had only water beforehand (and go easy on the calories the night before). Start by riding fairly steady - but not too easy - for 2 hours or so with just water, train your body to burn more fat and less glycogen.
• don't overdo the recovery nutrition. Again, real food is perfectly adequate.

Don't do too much per week or you'll get burnt out, ensure you do each session/ride feeling fresh. Get plenty of sleep. Don't fret if you have a week off the bike or eat poorly, put it behind you and get back on the wagon.

Pick a training plan either from Trainerroad or off the BC website.

Riding regularly every week will make the most difference, you don't necessarily need to batter yourself with intervals.  When I started training properly, following a plan (rather than what I fancied day to day), it was the regular riding that gave the biggest improvement from the start.

And if you can up the riding whilst not increasing calorie intake, the weight will fall off and add to the improvement.

I ride probably 6 days out of 7 but some of those won't be much more than half an hour to an hour easy spin.

I suggest getting a coach! You've already done the distance & must have reasonable condition so they will helpmake real improvements in your riding and time management as well as help plan other goals for 2017

No problems at all.  If you like riding in the cold of winter just go out and ride as much as you can.  If you prefer to stay warmer, jump on the turbo and do a training plan.

 Trainer road has 3 stage plans for most types of rider.  

Base plan, either sweet spot or traditional base work.  Build stage developing power and endurance power. Final stage tailoring to prefered discipline, time trail to sportive events.   Each stage is 4-6 weeks in length and come with different intensity levels depending on time available and recovery.

You don't need a training plan.

You just need to ride more, consistently... (also through the winter;-)

Missing a few details to be able to provide much input, but without knowing what cycling you do at the mo, how much weight you're aiming to lose, how much time you can devote and which turbo trainer you have....

70 miles and 4k feet isn't too brutal and it seems like you have realistic pace ambitions..? You have a winter for training, so

1 Have a look at Trainerroad or the like, and use that as the basis of your fitness training. Have a realistic look at training plans to build base fitness and then to cater for any specific aims (eg climbs) you have.

2 Get out when you can for longish rides, to get used to the type of terrain, the weather, the bike/fit, your fuelling, your gear.