Wobble2plank, not quite I'm afraid.
the IMC does not allow flight within airways
That's true, but:
this is a big point especially if flying anywhere near a major hub
that's not true. You can't use the IMC rating in Class A airspace, but that still allows you to get into every airport in the UK except for Heathrow, Northolt and the Channel Islands airports.
Oh, and having a full IR gets you 5 hours off the CPL requirements as well
I think (and I'd have to look this up to confirm) it actually gives you 10 hours off the CPL. (Are you getting confused with doing it the other way around? Having a CPL gives you 5 hours off the IR, maybe that's where you got your 5 from?)
Also the MDA/MDH for an IMC is, considerably, higher than an IR
That's true (almost, anyway). But on the other hand, if you're flying a single-engined aircraft (as most IMC-rating holders do) you wouldn't want to fly with a 200' cloudbase anyway.... what would you do if the engine quit in those conditions?
So, in conclusion, the priveleges of the IMC-rating really don't restrict the private pilot in a single-engine aircraft in any practical way beyond what he would be able to do with an instrument rating, other than that it can't be used outside the UK. But whichever rating you have, it's equally important to keep it current.
FFF
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