UKC

I tried to piece together a trip to the Dollies by train rather than flight.

Long story short - it was too convoluted to be realistic.  The Eurostar to Paris, Thello to Verona and then a string of badly-connected buses and trains to get to somewhere with only a €100 taxi to the valley to start the walk in... and 2 days each way.

So where can I get to for decent climbing without a plane/car?

There's a Eurostar to Lille and connection on to Grenoble (7 hours total from London; which is very broadly in line with flying); anywhere else/better?

Mountains rather than cragging if possible.

Have looked into this a bit myself as a way to try and reduce my carbon footprint (sadly it's hard to find like-minded folks). Here's some options to consider (haven't put any of them into practice so it's all theoretical):

-Ailefroide: you can get a night train from Paris (gare de Lyon) to L'Argentière-la-Bessée, then in high summer (July-August) a bus will take you all the way to the village/campground of Ailefroide. From there you'll have access to dozens of multipitch routes and mountain routes (plus sport climbing and bouldering). The bus even goes to the end of the road (Pré de Madame Carle) which is the starting point for some classic routes. Gear and food available in the village.

-Chamonix: will probably try that next year. It's a six-hour journey from Paris with two changeovers, then I reckon once you're in Chamonix you don't need a car with all the lifts and buses.

-Pralognan-la-Vanoise: train from Paris to Moutiers then bus to Pralognan. Food and possibly gear available in the village, couple of campgrounds.

-Presles: 2h30 journey from Paris to Valence, then if you stay at least a week at Bernard Gravier's place (Entre ciel et pierres) he'll come and pick you up. From his place it's a short walk to the rappels of many routes (+ a couple of sport climbing areas).

-Annot: I know you said you prefer mountains but the crack climbing at Annot is brilliant. It's a six-hour direct train from Paris to Nice, and then a 1h30 train ride (on the Train des Pignes) to Annot station, which is where you'd park to get to the climbing. Campground is 2km from the center of town/crags but you can find lodging closer to it.

-Riglos: haven't really looked into it but looks like there's a train station so could be an option

second vote for Ailefroide and Briançon area, I live here but have taken the over night to Paris and back a few times really easy, as well as bus option to Ailefroide hitching is quite easy round here.

Val di Mello is certainly possible with public transport. Albeit not sure, How easy getting to Italy is from UK. 

Train to Milan (thello) then another train to domodossola then bus to macugnaga. Gets you to the foot of the Monta Rosa and the alps.

Have you thought about going by road? There are some cheap bus options and car sharing is big in France. It's not too hard to find a BlaBla car. Il currently looking into going from Zurich to Spain and then back to the UK in half term. 

Also you could get the ferry to Spain and hire a car or hitch when you're there. Unfortunately you need to book really fr ahead.

Just had a look... London to Salzburg is around 11 hours, multiple options from here for Alpine bolted and trad rock. 

Friend of mine arrived here in the Champsaur day before yesterday by train from Inverness to Gap via London, Paris & Grenoble - 25 hours including a night on the Inverness-London sleeper. Unfortuantely the Paris- Briançon night train is only running a couple of times a week at the moment due to repair work somewhere but is expected to be back to normal in a few weeks (the replacement bus isn't as comfortable).

Train to Munich*, then regional train to Garmisch Partenkirchen (~1hr). Plenty of accommodation there and lift / walk up to the mountain rock routes around the Zugspitze & Karwendel. The train then continues down to Innsbruck, no doubt with more mountain possibilities.  Depending on your demands for height, the northern limestone alps are very doable by train & bus.

*You can do Eurostar to Paris / Eurodisney, then train via Stuttgart / Augsburg to Munich. You might have other options, but I've looked into getting there from western France and that's my option. 

Or.....Train up the Eiger from Grindelwald.

Or.... train to Kandersteg and the 3000m+ snowy mountains there for Alpine stuff. Accommodation in the village, camping too.

The only problem with trains is that tickets only come out 3 months in advance or thereabouts, which is a bit of a pain when trying to get cheap prices for connecting ferries or flights.

Have a look at the German Railways website for journey planning. www.bahn.de. Check www.seat61.com for tips on planning. I have traveled to Regensburg Bavaria via Brussels and Frankfurt in a day and I think the journey time to Munich will be similar and Tyrol Austria will be very manageable in a day if quite long. 

also have look at Interrail ticket options as they are may be a bit more expensive but you have a bit of flexibility about train booking. there's a ticket for 3 days travel in a month for 194 quid. Eurostar have an interail seat reservation fee of £29 on top of the ticket.  I haven't used this option yet but I'm thinking about it for my next trip to Bavaria.