Dismantle it. Just do it, it cost a tenner, whatcha got to lose ?
Start with the easy bits, seatpost, calipers, wheels and handlebars.
Handlebars and quill will come off together, just undo the centre bolt,, give it a firm tap to undo the taper and it should, albeit with a fight, come out the frame.
Disconnect all the cables at the calipers and at the derailleurs.
Eventually you'll end up at the cranks and BB. The cranks look like cotter pin type. Loosen the nut, not remove it, and tap firmly with a hammer to loosen them. Leave the nut on while tapping to protect the threads.. Because theyve probably been on years, the cranks may take some persuading.
BB will almost ceratinly be the old cup n cone type. If it feels ok, you could leave it..or strip and replace with a modern cartridge type.
Getting the paint off the frame may not be easy. My Raleigh Clubman was hard, so hard I gave up and had it sandblasted and powdercoated. Nitromoors just didnt touch it,. I tried sanding with emery cloth, it works well on the tubes, but its hopeless in corners and on detail work like lugs and joints.
Hopefully, someone will have a better method for paint removal, I struggled.
Go for it I say, its very satisfying.