Thanks for the helpful replies. A physical inspection showed nothing bashed or broken. On the basis of a little knowledge is a dangerous thing but no knowledge at all is worse, I found this schematc elsewhere on TM and some useful info online https://appliancesfirst.com/what-does-car-refrigerant-smell-like/ It's booked in to to local A/C place next week, I'll report back.

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Peter
2009 3-litre Roadster "Ivor", royal ivory / green