UK PAYG SIM including data...

Hiya,

Can anyone recommend a good UK Sim to buy, for use for a few days every 3 or 4 months (so nothing that expires or charges each month!), that has good rates for both text and data?

I currently have a Virgin PAYG by direct debit which is v competitive for calls but does not do data - and I am sick of lobotomising my blackberry whenever I travel! So I end up 'forgetting' to swap the Sims out and paying ridiculous international roaming rates so I can keep up with crucial work emails. And facebook...

BDP x