I'm assuming that the roofspace is a zone and that the mcp is at the loft door - this would be the exit from the zone down to the next level.I suppose they may have thought that if someone was doing hotwork up there then in the event of an accidental fire occuring the person heading down through the trapdoor hits the mcp.
As for getting a few extra quid - if there's a detector up there then there wouldn't be a lot of money involved in a mcp.
In reference to the weekly test it should be tested as part of the weekly test at some stage and,depending on the number of mcp's,this may equate to 4 or more tests on it per year - as you say,4 of the tests could be timed to coincide with your maintenance visit (as long as you can do your visit on the same day and around the same time each quarter.