I’ve got the OEM H7 units on my Shuttle, they are entirely adequate and though it is always nice to have more light I have never felt they are too dim. My last car was a Ford Galaxy with HID/Xenon lights which were brilliant but the VW OEM H7 lights really are quite good. I have never used the H4 units but from reading on here they sound awful. For a straight swap and £150 it sounds like a no brainer.
Your other options are to go with Transporter HQ units for £350 but they are just basically restyled H7 units. Or then you got to LED but you need deep pockets for that.... like £2-3k deep. No thanks!