Not a bad plan. A few comments though.
Initial class 1 medicals cost £400 when I did mine - so a little more than you budgeted.
Ground school - you are quite right in all your assumptions. The only thing you've got wrong, I think, is to concentrate on Conventry for distance learning. If you are forced to go the distance learning route, then one of the advantages of this route is that it doesn't matter where the school is located - it's distance learning!
Most distance learning courses will require 6 weeks off work - two weeks for the brush-up, one week for the exams, all multiplied by two because you have to do that for each module. If time off work is a real problem, look at LGU - you can get away with 3 weeks off with their course (one week brush-up and two days for the exams, for each module). Consider why no one else does the brush-up in this space of time if you look into this option though. Another option is to do module 1 this year, and module 2 next year, thus spreading your time off across two holiday years.
As for which ground school is best (it's not just the quality of the course material which counts, there are other factors - but that's being discussed on a couple of other threads at the moment so I won't go into details here), only you can decide that, because only you know what suits you best. Look at all of the schools, and make up your own mind.
You asked how long to spend on a distance learning course each week. How long is a piece of string? If you work full-time on your studies, you'll be able to pass the exams in a similar length of time to the residential course. If you can only spare a couple of hours a week, it'll take much longer. I usually spend around 15 hours a week, and it will have taken me exactly 12 months assuming I pass all my Mod 2 exams in Feb.
Have you got an IMC rating? I'd imagine that would be useful for flight instructing if you don't have an IR - it'll let you teach above a cloud layer, and you can even do some real IMC work for the instrument appreciation part of the course. Plus you'll be able to teach the IMC course later on, with more training.
Hour-building... if you only need 50 hours, then why not just fly at weekends? Since you say it will take you the best part of a year before you're ready to do the CPL, if you fly 2 hours a week you should make the minimums easilly, even allowing for the British weather.
Good luck!
FFF
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