Hello Steve076
I assume you are referring to the Brake Booster Servo unit. The Vacuum pump is fitted to the rear of the engine.
You are quite correct the seal/grommet is a permanent part of the construction of the very expensive brake booster servo.
A secondhand vacuum tube can be got from SMG Wolverhampton for about £25 to £30 and this includes in its construction
the NRV or Check Valve in its assembly. But assuming the NRV is working properly this isn't the bit you need.
You need the expensive Servo which can be got from David Manners and SNG Barratt plus others for up to £600 (not even Jaguar prices).
I am in the same pickle. My car is now SORN until I fix it.
Dave
