Doing away with it completely. I've gradually weaned the wife off the land line, we've had mobiles for years with inclusive minutes (me & the wife, the kids are both PAYG but £10 last 3 months +), and for all four of us the cost is not much more than BT's line rental per month. Only person that ever rings the land line is the mother-in-law and so she can ring our mobiles instead - not sure what call allowance she gets on her LL/Mobile though.
Only potential problem I can see is when the wife needs to get hold of the doctors she has to use ring back (constantly engaged), which is not available on mobiles - she'll have to just keep trying. If it does become an issue then I can get a line from Virgin, it's only £2 a month, but I'd rather not as the cost is already more with Virgin.
As for my VDSL speeds they've never been great, used to get 12Mbps upload but gradually its dropped away. Download has fluctuated up and down, been as low as 38 and very briefly around 60Mpbs when first installed, but was generally around the mid 40's. BS checked out the route my cable takes and it's length, which was 450m plus a bit from the last JB into the house, so 450 - 500m. But he couldn't see what the cable make up was, but highly suspect its is or has ally in it. Oh and being on ECI cab means that holds it back, prior to VM announcing their installation I was planning to get a new line installed, which would have been on the twin Huawei cab (hopefully) installed last year.