Yamaham PW 80 Help, advice and parts needed please....

Hi All

Just got my son a used PW80 as his very first introduction to the joys of
motorcycling, and hopefully 10 years of building up some competence before
he gets a licence for the road.

The bike was sadly lacking any TLC, a quick jet-wash showed it is in
excellent condition with even the lines of paint still evident on the
original tyres, I even got the original receipt from his Dad giving me
confidence it wasn't stolen.

I would like to do some DIY tinkering on the bike to keep the bike safe and
in fine fettle....

Any advice on any of the following (sorry in advance):

Tyre Pressures
Plug Gap (and type if just to check the right one is in)
How to get to the oil reservoir (under the seat) [previous owner didn't even
know there was one and pre-mixed the fuel/oil!!]
Anywhere good for parts and possibly servicing in West / Yorkshire
Carb adjustments - Perhaps the jet was excessive and I have got a little
water in the carb as it starts to splutter and die when off the flat (could
also be due to only 80cc and my lardy ass lol)
Anything else I should know and look out for.

Parts:
Exhaust / Silencer (previous owner removed it so it sounds like a big chain
saw)
Replacement plastics, looks like a wheelie went a little wrong and the rear
mud guard has been slightly damaged

Thanking you all in anticipation....

Lee
CBR600RR, RC45, NC35 and now PW80 )