Hi,
Good to hear you are thinking of an NPPL M with us here at Strathaven.
Simple answer is: sort of!
Longer answer, any hours done on a microlight count for an NPPL. If you haven't done your General Skills Test, then they will count towards an NPPL M or an NPPL SSEA (ie light aircraft).
So, if you had done 31 hours on a microlight C42, then you could do 1 hour on a Cessna 150 and then sit your GST and you would have a NPPL SSEA.
Alternatively, you can get your NPPL M on the C42 and do a three hour conversion course and get a SSEA rating added to your NPPL. There are people who specialise in this.
With an NPPL SSEA, until Easter 2017, you can get an EASA LAPL issued for c85 quid. No tests, no flying.
With an EASA LAPL, you can then progress to an EASA SEP if the need takes you. If I recall correct, you might have to do about 15 hours more training: but you could use this to start learning instrument or night flying, for instance
The above is all what is legally possible.
So people will point out, and rightly so, that you would be unlikely to be able to pass a NPPL GST in a Cessna 150 after just one hour in one, following 31 in a C42! You would have to allow yourself time to convert to a different aircraft.
Having said that, we have had quite a few people who have gone from here and done just three hours in a Warrior and then passed their SSEA test.
Hope that all helps.