[ben]

I wonder if these are rebadged Philips units. After all, Pye was acquired by them in the 1960s.
If so, you may have problems with crumbling gears and deteriorating erase heads. Quality of build took a nose dive in the 80s. Plus these radio-cassette units were pretty much the lowest quality as tape players go, aimed mostly at kitchens and teenage bedrooms. Add to that the fact it has been standing for years...
Some photos of the cassette mechanisms with the doors open might help confirm this.

If you cherish those tapes and are curious about the format, I would suggest looking for something a bit better and more worthy of spending time fixing up, to get the most out of them.