Welcome from Warwickshire.
Lovely looking car. Looks like it has had lots of care put into it already.
Roof motor - relocate it to the boot. Much safer there.
The N52 engine is reputed to be bomb proof but a few niggles to watch for.
Water pump as mentioned. Hydraulic valve lifters can be a nuisance. Vanos solenoids can stick. Easy enough to take out and clean or replace albeit fiddly. DISA valve can get dirty but unlikely to fall apart like other earlier engines. Cleaning it makes a world of difference.
Gaptek is a module that allows you to open and close the roof with the key. Again, fiddly to install but well worth it
