Really? An XC90, you sure you don't mean an XC70?
Like this?
https://farm3.static..._c6a9365d8d.jpg
That's quite interesting... In LAS, the XC70s are HART and Central Ops vehicles. Seems strange they'd be used as standard FRUs (or do SECAmb call them RRVs?). I would've thought the V50s and V70s would be the standard FRU/RRV.
I think the Ambulance Service for a UK mod is something you can go into A LOT of detail with, if you have the right knowledge. For example, in my personal mod, I have units with individual call signs and reg. plates that can only be used once, and extra units for everything you could possibly think of (HART, Officer, Unmarked Officer, Doctor/unmarked Doctor, HEMS Car etc. etc.). However it's one of those things where you'd end up with multiple vehicles ingame all serving the same purpose.
That's the one, I always get them 2 mixed up. Its always doing blue light runs through Immingham.