I don't have my Bentley manual here, so can't check to see if the upper
strut mount can be replaced safely without a spring compressor. If a
spring compressor is required, then removing the spring and checking the
strut cartridge would be wise anyway. It would also be wise to check
that everything was reinstalled correctly when the seller replaced the
springs. It would have been logical to replace any bad strut cartridges
or upper strut mounts then, so the noise and shaking should be cause for
concern about proper reassembly. Check also to see that the springs
have short lengths of hose slipped over each end of the springs to help
reduce noise. Good luck.
Dale Scroggins