problem taking home phone number when moving

zzzzjohn

I originally had a BT line, and transferred to tiscali to take up a broadband package. i am now moving a hundred yards up the street and asked tiscali to transfer my account and my phone number. I was told i couldnt because it was originally a BT number (weren't they all?) What i appear to have to do is cancel my tiscali contract, at a cost, take out a BT contract, then apply to move the number, then I'm stuck with BT or have to buy myself out of that contract to get back to tiscali.
does anyone have any advice as to how to avoid all of this? ( i dont want to change my phone number~)