I got my Silver 'C' and converted it to an NPPL. I don't think you can convert a solo licence. It took about 16hrs in a Cessna to finish the NPPL and you have to do all of the PPL exams.
Essentially no, a giding license has no bearing on your group A license. However (as above) under certain circumstances it gives you a few hours towards a group A license. Probably more expensive to pay for all the gliding than just get a PPL normally, though.
A.L.
'Flying is really the art of throwing yourself at the ground and missing' (Douglas Adams).
With a BGA gliding licence you can use the 10 hour route to gain an NPPL (SLMG). This training is available through approved BGA Clubs. Differences training is then required to add the SSEA rating to the licence.
There is no provision if you wish to obtain a JAR PPL (SEP). The 10 hour route with Silver "C" ceased with the introduction of the JAR REGS.
Do you need to be named Smith to be in this Forum?
I am a motorglider pilot via the PPL route and watched the developments over the summer - which closed most of the UK's motorgliding fleet to JAR training. The NPPL route and SLMG still look good if not the only route and I understand you can ask/apply for conversion from SLMG to TMG after 75 hours, which may be a 'back door' onto the PPL if I understand it right.