on my 4th geometry alignment in 4 months, is there anywhere in the world that can set geometry correct AND have the feckin' steering wheel pointing straight????? on my 3rd garage now (if you want to know where to avoid in oxfordshire, including 2 supposedly well regarded garages then let me know!) and having just had it supposedly set right this morning on the drive to work its still wrong, so have to go back later, again. It just seems to crab to the left in all conditions. So frustrated right now.
Have the garages you've used been doing a full 4-wheel alignment or just the front tracking? The reason I ask is because the 'crabbing' symptoms you're describing, together with the steering wheel being off-centre, are exactly what would happen if the front tracking was done correctly, but the rear wheels were pointing either left or right of where they should be. It could be either or both of the rears causing the problem.
What's required to correct this is a full 4-wheel alignment using (ideally) a Beissbarth alignment rig or (not quite as good) a Hunter alignment rig.
During a full alignment, the centre line of the car is 'discovered' by the computer and optics. The rear wheels' toe-in/out are then aligned to the virtual centreline to ensure the rear wheels aren't steering the back of the car. Next, the rear cambers are calibrated to give you optimal grip and tyre wear. Once the rear is all properly aligned, the front wheels' toe-in/out are aligned, based on where the rear wheels are pointing. This is done with the steering wheel locked in the straight-ahead position so it has to be properly centred once the alignment is completed. The front cambers can also be equalised and adjusted (within limits) by moving the front subframe. This will again give best grip and tyre wear.
The whole process can take a good hour or few as altering any one parameter on the suspension will have a knock-on effect on the others. The operator will likely have to go around the car two or three times before all the adjustments 'funnel-down' to exactly where they should be. This makes such an alignment costly, but well worth the trouble. Why? Excess tyre wear will disappear. The car will steer straight and true. The steering feel, turn-in, adjustability through a corner and overall grip will be vastly improved. Finally, your fuel consumption will be appreciably better as the car won't be dragging its tyres sideways along the road any more. The savings in fuel and tyres will pay for an alignment quickly enough, but the joy of having the car steering properly is well worth the financial pain anyway IMHO.
As to where to go. The only really top notch alignment specialist I know anywhere near you is Center Gravity near Tamworth. Chris who owns CG is practically worshipped amongst the Porsche community for his ability to set-up a car correctly. Whether he would do work on an Alfa, I'm not sure. Unfortunately I'm in Manchester so I guess my local alignment specialist (who also has a full Beissbarth setup) isn't going to be any use to you.