Hi Joe.
I'm going to assume from the "b reg" bit, you're in the UK.
There's a very active MZ rider's club in the UK which is more focussed on the 2-strokes than this forum (no offense guys), but they're not really very internet based, which is why I'm on this forum... There are meetings all over the country though. Try this link:
http://www.mzridersclub.co.uk/frames.html The magazine's pretty good too. It'll take a bit of time to access but the support is there, just takes a bit of effort on your part to get to. Also the magazine runs a for sale/wanted section and these old bikes do move around. A non-runner with no tax/mot is probably still worth upwards of £50, nearer £100 if it's substantially complete (I'm afraid I can't see your pictures for some reason)
Let us know whereabouts you are and if you decide not to keep the bike, I'm doing a bit of a restoration project myself at the minute and might be able to have a discussion with you... No promises though!
I haven't seriously tried to get any parts yet (I'm still in the dismantling stages of the rebuild) but these guys in Germany
http://www.akf-shop.de/shop/index.php/cat/c178_MZ.html are reckoned to be pretty good.
HTH, and welcome to the forum!
:@)