I;m an Ausie and have allway been confused by British licence terminogy.
Join the gang, mate!
Back in time, when life was simple, you could have a British (sorry, UK) PPL, then a CPL then an ATPL. You needed 700 hours to get a CPL. Whilst a lucky few got taken on as cadets by an airline, most folk get a PPL, then an instructor's rating in order to get paid a bit while they accumulated the 700 hours and did their self-study for the exams. By that time, they were reasonably good at flying and the CPL flight test was usually conducted in the type they were earning a living on, not a problem.
THEN, someone decided that you can't have people being paid to fly (i.e. instruct) without a Commercial licence so a rule was made that instructors had to hold a CPL. Now, a reality check was made - we had loads of instructors who would be out of work and effectively flying training for PPL would vanish. Sooo... a typical British compromise was dreamed up. All these PPL instructors (some with huge experience and many thousands of instructional hours) were 'given' a CPL without taking a test or passing any exams. This was labelled the 'Basic Commercial Pilot's Licence'. Having dreamed up this licence to pass on as 'grandfather' rights, it was decided that any new instructors who didn't want to get a full-blown ATPL could also get a BCPL by doing the CPL exams and passing the CPL flight test. Having done that, you could THEN go on to do the Instructor course.
With me so far? Right. We now have TWO groups of BCPL holders: those who had them dished out 'cos they were instructing on a PPL and those who did all the CPL stuff, only at 150 hours instead of 700 hours. I'm in thet latter group, by the way.
You could also get a BCPL on a less stringent medical; we used to have 3 classes of medical in the UK, Class 3 for PPLs, class 2 for BCPL holders and Class 1 for Air Traffic Controllers and airline pilots. 26 years ago, I was told I couldn't get a class 1, now I can, too late for an airline job but now I'm learning how to be an instructor. (On-the-job training - marvellous!)
It was further felt that the holder of any kind of commercial licence ought to be able to fly by sole reference to instruments, so you have to have a current IMC rating to hold a BCPL (see below for the IMC rating!!!) Most of my instructor colleagues have frozen ATPLs (i.e. they've done all the exams and flight test, but haven't got the hours yet). I stand to be corrected, but I don't think they have to have a current IR in order to instruct, whereas I believe that I have to keep my IMC up to keep my BCPL and thus my instructor rating valid.
Ratings and licences.
A licence is the basic bedrock document. In order to exercise it, you have to have some kind of RATING, such as Single Engine Piston (SEP) Multi (MEP) Flight Instructor (FI), Instrument Rating (IR) etc. For instance, you do your PPL on a Cessna 152 and get a SEP ADDED to your PPL on inital issue. You can then ADD further ratings to it. If you move up to flying 747's on an ATPL licence, and get the appropriate ratings for that and want to fly a C152 on your days off, you still need to keep up your SEP rating as a separate deal.
Now, IMC and IR.
The Instrument Rating entitles the holder to fly a suitably equipped aircraft in controlled airspace by sole reference to instruments. Obtaining this rating for ordinary folk is hugely expensive and time-consuming and a major challenge for the mind.
With our typical British weather, many years ago wise heads thought it would be a good idea to teach PPLs a bit more about how to avoid bad weather and how to get safely out of it if you flew into cloud. Thus the Instrument Meteorological Rating was born. It allows you to fly by sole reference to instruments OUTSIDE controlled air space (CAS) and on a few occasions inside CAS, to land at some airports with suitable instrument procedures (and a few other occasions as well). It's NOT a cut-down Instrument Rating, though I know some people who think it is and use it as such. It has been tremendously successful and holders of the IMC have a fantastic safety record - only one accident as far as we know where an IMC rated pilot has flown into a hill in cloud in the past 40 years. The IMC course is at least 15 hours and a 90 minute test, ground school and an exam. Easily do-able on weekends or days off, you don't have to take weeks and weeks off work to do it. It is only valid in the UK, it magically evaporates half-way across the English Channel. On the other hand, it turns back on again if you're coming back from France in dodgy weather!
On the occasions where I've used the rating, I've mostly called up for a Radar service; you don't have to file a flight plan to do this, just call and tell 'em what you're doing and where you're going and they'll keep you advised of traffic that shows up on their 'scope.
There are hardly any airline cadets any more. You either scrape the money together (or borrow it) to get a frozen ATPL then instruct to get the hours (the self-improver route) or you get your parents to buy you the full course (integrated course). There are enough of the latter to save the airlines having to spend out on training pilots themselves.
Any more questions, please ask!
TheOddOne