I'm presuming you already hold at least a JAR CPL and IR, and that all you're wanting to do is add your Dash 8 type rating to this licence, if so here's the answer regarding the UK requirements:
LASORS 2010 Section F9.1
TRANSFER OF TYPE/ CLASS RATINGS FROM A NON-JAA STATE LICENCE
Type Ratings (Aeroplane)
A type rating endorsement on a licence issued by a non-JAA State may be transferred to a UK issued pilot’s licence, subject to:-
i. 500 hours flying experience as pilot on type, operating as P1 or P2 appropriate to the rating required.
ii. Operational experience as pilot on type within the preceding 5 years.
iii. Pass a Proficiency Check on type with a JAA Authorised Examiner.*
iv. Have met the requirements of JAR-FCL 1.250 and 1.251 as applicable, including knowledge of aeroplane performance appropriate to that type (please refer to Section F4 - Knowledge of Aeroplane Performance), and the theoretical knowledge requirements of JAR-FCL 1.251 and 1.285 as applicable.
*Should a synthetic training device be used, the device shall be approved by a JAA Member State that has been recommended for mutual recognition.
http://www.caa.co.uk/docs/33/SRG1119.pdf + Fee of £119, sent into CAA with original ICAO licence with Dash type rating endorsed, and original logbooks showing +500 hrs on type. If you turn up at the CAA before 12 noon, they'll stick it on your licence the same day too.
http://www.caa.co.uk/docs/175/srg_lt...ection%20F.pdf
If you don't have a UK JAR licence, or any JAR licence, and need to convert that too, let me know.
VJW