The specialists are MDRS in Leadgate Co. Durham
Anyone who is my situation where due to mobility issues I can only do the simplest of maintenance tasks any 'proper' jobs I take it to a local specialist I have recently found. I called in on spec one morning with an intermittent but regular reduced power warning. Now they didn't know me from Adam but the boss (Dave) put it straight on his diagnostics, found the fault code, read the live data EGR valves not fully opening or closing. Wouldn't accept any payment! So I booked it in for the work so probably his generosity was actual good business sense. Deleted EGRs and the TPMS and a re-map for what I thought was a reasonable price. Took it back to them this week for front and rear diff oil change, transfer case oil change, gearbox mega flush (they use the same machine as the renowned 'Bodsy'), rear discs, pads and handbrake shoes and the full Dinitrol rust treatment. Total cost for all of this was £2.200 which I think is reasonable considering that my local non specialist garage wouldn't do the EGR and TPMS or offer the other services except the brake rebuild.

Gotta say I am well impressed with their level of expertise and customer service.
I have no connection with this company I just hope this helps anyone in the north east who needs the services of a specialist