Re cost. I ended up with quotations ranging from £342 to £450. I went with Heritage at £345 for reasons stated above. I do have other vehicles to drive and max no claims although Heritage say this does not affect their quotations.
My Porsche Boxster S which I sold to make room for the AR-P4 was costing me a mere £220 fully comp with SAGA albeit the insured value was a lot less.

3.7 Roadster
Porsche 964 C2
JCW Mini Cooper S Cab
BMW F750GS
+4 4 1995-2002 / LM 62 +8 2002-07