Welcome. Good choice of car ( I have one!). See mine here:
http://s1312.photobucket.com/user/JPS130TC/slideshow/Detailed Strada
The NorthWest is a BIG area. You really want a garage that knows about old-school cars and carburettors, especially prepared to use care and patience on the car rather than rely on diagnostics and computer parts finders ( parts are hard to come by), not the latest Abarth garages which just bang out new modern Abarth badged 500s/ Grande Puntos etc bristling with electronics.
I don't know the NorthWest at all. Hopefully somebody up your way will see your enquiry and help.
However, depending where you are in the NW, it may not be too far for you to go over to
Walkers Garage at South Otterington in North Yorks. It would certainly be a nice journey! Though really a FIAT dealership, they are the acknowledged North of England experts on Lancia Deltas, so would almost certainly have the knowledge/skills/techniques to sort your Abarth- at a cost!
One of the better-known and highly regarded specialists in Strada Abarth are
Middle Barton garage,but they are in the Cotswolds- a long haul for you, but perhaps worthwhile if you want a really good job.
For other info,consider the owners' club at
www.strada130.co.uk, perhaps someone on there ( there are only around 200 registered members,but only about a dozen reasonably regularly active) - perhaps someone on there may be from your area, or have knowledge of garages up there?
Good luck.Put some pictures up of the car....................