There’s some good stuff here, thanks for your help.

Spin – I might hit the turbo, but as I like to enjoy my riding (even the uphills), it won’t be a habit – just if we get snow and ice between now and August!

Mrmo & others – I guess I am missing the target a little by trying to recreate the climbs here – I think the alternative approach of reps on smaller hills is more appropriate – Bredon Hill and Edge Hill are 2 local hills that offer 100m climbing at 10% or so, so I’ll be building up on those. I have been doing some weights and leg strength work over the winter to prepare my legs and upper body for the pain of 1000m climbs and 1000m descents – that has started to work well already.

I have the Dragon Ride in June, and have done that a couple of times, so I know the climbs it offers are about right.

For the effects of altitude, I am going out a week early, so will be getting a few 0.5-1 hour sessions as high as possible during the preceding days.

Hadn’t thought of time trials as a potential training aid – I’ll search out some local 10 and 25mile TTs and have a crack. I’ll be doing a few MTB races also, but these are only 60 – 90mins long, so limited benefit, but any riding is good riding.

Whatnobear – I have done the climb to Wanlockhead – during a Lejog 6 or so years ago – was quite long, and as I was encouraging a mate who was having a bad time, it didn’t feel anything like 8 miles. Did take a while though at less than 10 mph. The descent the next morning was fun though!

I might hit the turbo

Actually, thinking about it if you don’t have hills nearby it’s probably the best way to replicate a 1hr plus steady effort. Provided you have the will power. I definately don’t!

As above for Great Dun Fell but a trip to the North Pennines in general. Several circuits of the heads of the Dales ride plus or minus variations would give you some big climbs. The core ride goes between Teesdale, South Tyne Valley and Weardale – no real best place to start but for arguments sake try Langdon Beck.

B6277 from Langdon Beck to cross roads on Garrigill to Nenthead Road, over top to Nenthead. Nenthead on the A689 to St John’s Chapel then over the top to Langdon Beck. Gives you a couple of big climbs and the joint highest classified roads in England. Climbing is probably harder going anti clockwise – opp way to described. Route is 41km with just under 1200m of climbing. There are variations you can do on this by adding loops to Allenheads, Rookhope, Blanchland.

The roads with big climbs on them are:
B6276 – out of Brough is a long grind rather than steep, teesdale side has some short sharp climbs. Watch out for the bridge chicanes – especially Grains o’ th’ Beck.
B6277 – steady rather than steep, broad and well graded.
B6278 – climbs on either side of Stanhope and Bollihope are fierce
A689 – as on above route

For the effects of altitude, I am going out a week early, so will be getting a few 0.5-1 hour sessions as high as possible during the preceding days.

Just make sure you give yourself a good taper. Personally I’d be resting for at least a couple of days before hand. Sleeping at altitude is probably more important than training at altitude.

I read about someone who trained for the Marmotte whilst living in London with turbo sessions and a big ride once every 2 weeks

Exactly, its a common misconception that you need to train on hilly UK routes to prepare for alpine climbs- it helps but you don’t need it. 1 hr on the turbo at threshold with no fan will give you a taste of what its going to be like.