I've a similarly aged Pentax, an MX model with f1.7 50mm Pentax lens. (I've had it since the 1990s)
I've used it recently on a couple of model shoots with my dSLR as the main camera. (the models have been intrigued by it)
Poundland has been stocking both Kodak and AGFA films with a decent shelf life. I don't need to tell you the price
Snappy Snaps are reasonably priced for their developing and printing, and will also scan the images onto a disc (36 colour film D & P & CD for £12 ish)
There's a few of us in my local camera club with interest in film developing and printing, and I'll hopefully learn that art through time.
There's a recently formed group on facebook for film users. PM me and I'll certainly send you the link.
Gerry