This topic has been covered before.
The C208 isn't considered a MPA (multi pilot aeroplane) in the UK.
You'll need to do the medical at Gatwick.
The 14 exams, go to Bristol Ground School to do them in the shortest time. Note, you'll have to really work bloody hard to do it.
Flying? To appease the CAA you'll have to get a letter from your company stating that the time in the Twotter and the Metro was done under 2 crew ops and because of national law. (eg CAO 82.3) That should cover you for the MCC.
So you have 2 choices. 1. Do a type rating on a JAR 25 MPA aircraft and go straight to an ATPL. Looking at ~£10-20K plus CAA fees.
(Cost depends on the type)
2. Do the abbreviated IR with CPL. ~15 hours or so. This will give you a CPL/IR.
Aircraft category. JAR 25 MPA etc. See
JAR-FCL 1
Conversion and the UK CAA's verdict
LASORS Esp Section G.
Note, these are rather large PDF's so I would save them to your computer and peruse at your leisure/peril.