I'm also in the UK using T-Mobile Payasyougo on an unlocked SE 610 (was virgin). I just use the default settings from the mobile operator setup, and paired my phone oiver bluewtooth and it works flawlessly. Using Web n Walk for £1 a day.
If you go into control panel, and select tools, mobile operator setup wizard from the menu, it'll guide though though it, and set it up for you.
Gaz