Do the Cossie 4-pots have the same mounting pattern as bogo Sierra ones?

yes but the bolts are M12 (instead of M10) and they have plain holes in the caliper (the cossie uprights have the threaded holes)
also the offsets a bit different on the discs, thy can be fitted but its a bit of a fiddle

I've got a set of rusty ones if you want to borrow them

Cheers Robert! Can you PM me your mobile number and I'll give you a bell.

text sent (unless you've changed your number)

Received... cheers!

ofset is also different on them so you will need to grind part of the calliper & upright to get them to line up correctly with the discs