I did mine (the cheap way) on Sunday having been 'going to do it' for months. Very simple, but there are caveats depending on which BT master socket you have. Initial response was drop in line speed

, but I obviously need to wait the statutory ?3? days for BT to adjust to the line change. Will let you know. Top before was 2.3MB.
EDIT: Fom 680 kb last night 'post-mod' I am going through 1.8 mb this pm. Fingers crossed!