If you're looking for local area info, it's always worth trying the local
register office sites, where they exist. This marriage shows up on the free
LancashireBMD site, with the matching of the names; and you may be able to order
direct, via that site, for the standard certificate fee of £9, though they do
charge an extra £1 for paying by credit card.
Alternatively, the FreeBMD site also shows the marriage and gives you the
matching name. With (or without) the reference info on FreeBMD, you can order
directly >from the GRO, and pay by credit card, for £9.25.
Unless you want to pay a great deal more for the same thing, I would recommend
that you avoid intermediary services which will be doing only what you could do
for yourself, but for a substantial mark-up.