We need a front drivers side brake caliper. Hubby managed to source a remanufactered one, but it has gone in to be fitted today, and it was the wrong caliper - apparantly the new one was a single piston caliper and we need a twin piston caliper (I've got no idea what I meant then!

)
How do I go about sourcing the correct caliper - poor Jonnie needs one - and as hubby is in work from 6:45am - 7:15pm, he has no time to source one, so I've got to try to get one - which isn't easy when you don't know what you're on about!
Pleeeease can someone help me out?

...and point me in the right direction?
Thanks guys