This slang is actually used by many authorities around the world for a CPL with ATPL theory credit.
This is simply the next higher theory for a lower licence. the ATPL theory includes the IR theory. However, as you do not need an IR for a CPL, you will hold a fATPL as soon as you have passed your CPL flight test, no need for ratings to be added like the IR or ME or night.
The MCC is not part of any licence, and is therefore not a requirement for any licence whatsoever. It is simply needed for people who do not have 500 hours of experience on aircraft that have to be flown by two pilots by regulation. And yes, this could in theory be a C150, (however, the smaller an aircraft the more difficult it would be to justify the company requirement for an additional pilot).
All this information comes from my personal copy of the JARs, which were brand new last summer. So I stand co be corrected. However, the UK CAA makes their own rules, not necessarily JAR at all, so you'd need to check the
LASORS
My personal advice would be to get a PPL from a non-JAR country, as you'd loose a JAR PPL once you get your JAR CPL (eg. an FAA one, as it doesn't expire), and, when the time comes, do an MCC either on a cheap side, or, if you can afford it, on an aircraft a bit more interesting. - There are MCCs from £1000 to £4500 (and believe it or not, the cheapest I found was a full motion turboprop airliner with a national airline, whereas the most expensive one was a jet without motion!!).
This was two years ago, so things will have changed and you'll need to shop around...
Ah, just saw you got the PPL already. Well, at least hour building abroad should save you a bunch.
hope this helps
regards, IP