Noth South,
An instructor should never assume.
It wasn't a UK requirement. Then you know that I am not from the UK after all.
I would not be happy with CFIs arbitarily making the requirement as it would only be for money and not safety reasons. That is why the JAA / EASA are the people to inflict such a minima if it can be shown that there is a need. 30 it probably OTT but 15 can't be that far off the mark as a minimum. Remember that it is time on type and not necessarily instruction time.
If you want to spin - get Send Clowns to fly with you. He may never have flown the type but you should feel very secure after an hour of circuits prior to climbing up for that first spin.
Perhaps organisations are using the "trial pleasure flight" in order to give instructors new to type more experience. No bad thing but how many instructors teach steep turns or PFLs on a "trial pleasure flight"?
Regards,
DFC