Thanks for the suggestions,
having tried several without success I googled it and tried a suggested method of reheating it to release the bond. the jam went dry and brittle and was easy to scrape away with a palet knife. I'm giving it a soak with soap powder now and may try more oven cleaner before re heating it again.
Buffy
Careful if the pan is aluminium & you're thinking of using a caustic oven cleaner the two are not compatable and may also produce nasty toxins in cooked stuff after.
An old well tried working idea for cleaning any pan with burnt offerings on the bottom is an egg cup or so of fine sand and scrub it in with a block of soft wood along with a bit of soapy water pus elbow grease along with lots of repeats and rinsing with cold water.
Some dishwasher powders and dishwasher tablets are also fairly good at loosening things off but watch out not to use your bare hands when using them . Wash any residues off your skin immediately , also read the instruction some say don't use on aluminium items.
If you are indeed using an aluminium pan & it has a thin bottom insteead of a more modern 1/4 inch thick heat dissipating base ...perhaps think along the lines of getting a decent loud timer then cook & test the jam in timed 4 minute boils , get a sugar / jam thermometer (£6 ish ) off the internet and also a heat diffuser pad/screen big enough for the pan to sit on whilst cooking / boiling the jam .