I'd forgotten Cobham - they are relatively recent to the area though and mainly battlefield communications stuff as far as I'm aware (at least in Blackburn). Never been in there myself but I know people who were involved when they took some of the stuff from RO Blackburn.
I take it you mean Mercers? I know the shop in the town centre and I know the trade place in Pump Street - I get steel and ally there on occasion.
MBDA is the place on (or just off nowadays) Lostock Lane. The old factory was emptied out in the late '90's and everything moved into West Block or the south-site. West block was sold a few years back and was demolished last summer so we're just on the south site nowadays. Even that's only for the time-being as we are moving down the M61 to a new build on the old open-cast mine at Cutacre.