I have done a trial fit for the top strut brace and realised the coolant expansion tank is too high for it. Is there an alternative for a Mk2 or is there a way of lowering the existing tank to clear the brace?

how much clearance do you need?   spose you could undrill the bracket and move it down a bit?

The clearance needed would be about 20 mm.Yes I was going to look at that if the water drains back into the system with the tank in a lower position. Also I don't know if it is going to clear the brake servo but that is another story.