According to the following link, Bosch and Varta batteries are the exact same product (apart from the badge!):
https://www.batteriesontheweb.co.uk/bosch-versus-varta-batteries/
For a competent garage in Bedford I'd suggest Enterprise Motors on Dean St. They've been around for many many years. I've been getting my MOTs done there since 1986 (even though I live in Huntingdon now) because they do a thorough but honest job.
I think the GT may be similar to the QP, in which case you might find this useful:
https://www.sportsmaserati.com/index.php?threads/new-aircon-fan.27224/#post-650468
Scroll down to post #4.
Problem was similar to yours, just stopped working one (hot!) day. As metioned in the post the...
I did mine with one of these: https://www.amazon.co.uk/Sealey-VS820-Clutch-Bleeding-System/dp/B000ROARTI
Much easier than pedal pumping and therefore no risk to the master cylinder seals. You could do the job on your own with one one these but I had a helper watching the fluid level just in case.
I think the fan will still be on the passenger side on a left hand drive model. The drawing on Eurospares seems to suggest that:
https://www.eurospares.co.uk/parts/maserati/qtp-2005-42/interiors/a-c-unit-dashboard-devices-46340
The fan is No. 6 in the drawing.
No idea if there's a relay. I...
I had an issue with the air con fan on my QP (2006). 'Turned out to be just a tarnished connector. Check out this post for more info:
https://www.sportsmaserati.com/index.php?threads/new-aircon-fan.27224/
I think you'll need to get the rear shelf out. Have a look here for a good how-to:
https://www.maseratilife.com/forums/qp5-2003-2012/49505-2009-qp-seat-removal.html
Scroll down to post #10.
'Sounds like what happened to mine (QPV rear door). It's a bowden cable system that goes through a plastic scroll on the motor. The cables are secured to the mechanism with plastic clips that are a known weak point. One of the clips gives way and then the scroll lunches itself on the cable if...
You'll probably need to remove the plunum. Have a look at this thread:
https://www.sportsmaserati.com/index.php?threads/4200-oil-pressure-sender-removal.7556/