Seen as a notice on chalk-board at entrance of T-Mobile shops:-
T-Mobile SIM only for £10.21 monthly (12 month contract)
Inclusive 300 minutes and 300 Texts PLUS a Flexible Booster.
In addition to allocated 300 mins plus 300 texts, choose one of the following "booster" options:-
Internet Booster (unlimited but please see below)
Unlimited Landline Talk
Unlimited T-Mobile Talk
Flexible - you can change your choice of Booster every 30 days.
Not shown as available on-line.
Not sure how long this offer will be available from T-Mobile shops.
You can browse and email as much as you want.
There is a 500MB allowance for streaming videos and uploading and downloading files. If you hit this limit during the month, you won't be able to do this stuff again until the next month.