I use boiler guide, actually on an install this week from them. Any dud leads ie: wrong number, no replies etc then they do refund (I have had about 4 duff leads) also usual problem with potential customers who think replacing a back boiler costs £1000 all in lol. This is the first install I have got the nod on through them and it was a last chance before I closed the account!
How long have you been using them and how many leads roughly did you buy?