Hi Phil(?)
For a start £600 sounds like a decent price for a reasonable project assuming pretty much all there, the interior is not a basket case and the rust is not too terminal or extensive. If you are doing it yourself, then that will help no end.
The 1300 was the odd one out in the engine front, but one or two owners on here who can help with identifying what it had originally. On the ignition, check the earthing as with all old cars. Personally I would look to add an electronic unit to the points which keeps it simple, but avoids the burning issue of the points etc.
Some photos would be good to see.
I was wondering if this was Niels's old car, but then realised being off the road since the 90s it could not be, which given the last photos of it is a good thing!
I have some spare indicator lenses and may have the air filter you need, but would need to check which you have as there was more than one and no idea what the 1300 came with.
All the best with the restoration.
Peter