Microlights are good fun, cheap, and I'd be as reluctant to give up my microlight flying as my "group A" flying. But, given a choice, the microlight flying is much cheaper.
I do both as cheaply as I possibly can in syndicates, microlight flying costs me about £23/hr, group A about £60/hr.
If you've got 52 hours, then presumably you aren't far off your JAR licence? If so, you'd be better off finishing that, then doing microlight differences training; the alternative is going to be logging at-least 25 hours training in microlights, which is going to be significantly more expensive I'd have thought. With the differences training (probably only a few hours for a 3-axis microlight), you just have to keep microlight currency, then if you want to fly group A again, re-take that skills test in a few years.
You asked about the Microlight equivalent of Trevor Thom? It's a book called "The Microlight Pilots Handbook", by Brian Cosgrove, costs £20, and covers the entire groundschool syllabus in one volume - infinitely more readable than TT. Make sure you get the latest edition (Amazon is usually the best bet, or one of the many stalls at the PFA rally).
For types, take a look at
this thread which covered the subject quite well.
G