I
think it's a Pentax-K fit, so although You can adapt the lenses for NEX and Micro 4/3rds, and they'll work on Modern Pentax DSLR's as is, the lenses are nothing special (Although it's hard to fuck up a 135). £55 is a little steep, but assuming no stick apertures or fungus, it's not a wallet raping. If you find you like shooting on film, I have spare PK lenses You can borrow.
I do use film , a weighty EOS1 with "power grip" (
www.mir.com.my/rb/photography/hardwares/classics/eos/EOS-1/), sometimes underground, but
practice before you drag it underground. Light painting is hard if You can't see the results immediately, and decent film and processing are not cheap.