I'm looking to do a trip in march, looked at Switchbacks but they dont open till april, so what about Basque MTb do they operate that early? What is the climbing/uplift ratio given that I am a fat bastyard?

Any other suggestions?

Speak to Alan at Sierra Cycling
http://www.sierracycling.com

Their trails are a nice mix of climbing with lots of downhill, with minibus uplift in the morning.

Will be heading out in May to see the guys for my 6th visit

I've never ridden there but there has to be some good riding in the hills around the costa brava, I was there last month & saw a lot of MTB parties going out. 8)

sierra nevada is mint – hard but awesome scenery

looked at Switchbacks but they dont open till april

Switchbacks are open year round, except for August, no?

No and yes. See communique from Isabel at switchbacks below.
It was the xc am bit I was after.. (Although I would do the dh if I could a) persuade my co travellers, b) afford the 200 odd more euro, a 40% price increase)

Thank you for the enquiry. Would you be able to make it out a bit
later in the year. We don't normally open our XC/AM location till in
mid April, Bubion being at high altitude trail access (because of
snow) can be a problem in early spring. We run our DH holidays in
Benalmadena (Malaga) during the winter, for more info:
http://www.switch-backsdh.com

Pretty sure Ciclo Montana would accommodate u in March.

We went with pure mountains. Best holiday I've been on going back in 2011 can't wait. Amazing riding, accommodation, food and drink (which is all inclusive)

I went with Sierra Cycling last March and it was the perfect time of year I'd say – rode all day in short sleeves but it was never uncomfortably hot (max 25 degrees or so). Warm enough for topless sunbathing down at the beach if that's your thing too 😯

I was talking to a Basque 2-3 weeks ago about riding there in March time and she put me off – weather is still very cold (though we might still think it shorts and T-shirt weather!) April was the earliest she suggested with May better.

I have ridden near Benidorm late Feb / early March and the weather was nice during the day and chilly in the evenings. Southern Spain may be your best bet.