It's a mk3 and it does have something very similar to ISO connectors. Unfortunately I don't appear to have a decent radio cassette with an ISO connector.
An iffy one worked at first but drained the battery as the cars clock stayed lit up with it in place. I switched the perminent and switched live feeds around which resulted in it not working, it switches on but just plays static.
I have a couple of CD players but the local roads are too bumpy to use them.