I have a Pocket PC connected to the T-Mobile Business 1-Plan tariff
with the old style Web'n'Walk for an additional £7.50 a month (less
25%).

I however also have a laptop with a built in PCI Express data card
which could offer me HSDPA access with a suitable sim.

At the moment I can access the internet via my laptop using bluetooth
to the phone but it's unreliable, phone reception near the laptop is
poor and it's a real PITA. Swapping sims between the two devices isn't
an option as I need to remain in phone contact.

I spoke to T-Mobile about getting a Web'n'walk SIM added to my account
that I can use exclusively in my laptop and the best they can offer is
a mobile broadband at £20/month with free usb dongle I don't need.

So what's the most cost effective way of getting occasional (2 - 5
days per month) 3G/HSDPA access from a laptop.

Is a PAYG sim with daily "internet" bolt-ons feasible / allowable?
i.e. T-Mobile with a 1 day / 5 day Web'n'walk pass.

Are there any Sim Only data only contracts which charge £10 or less
per month, allow laptop use, and have a 1GB+ data allowance?

What other options are there?

TIA - Rufus