I know how you feel about your Z
@Shelly and I feel the same frustration as I’ve been without mine for ages and ages while its worked its way up a waiting list for work to be done. My beautiful Z is, at long last, in the workshop having the works done - flies the flag

My car’s delay has been that the business is specislist and very few do what it does so hence a waiting list.
I wonder about your garage, though. Is it prioritising quick turnaround jobs ahead of your Z? Is it capable to do the work? I know this is a basic question but there are far too many garages out there which will say yes they can do the work and they lack the expertise. This means they do a rubbish job and the car owner has to get the work done properly elsewhere.
If this were my Z, I’d look at other options and get it moved to a business which will do the work your beautiful Z needs as it arrives into the workshop. It’ll be worth taking the hit of £100 transportation fee to get the car back on the road.