http://www.speedflowshop.co.uk/index.asp

http://www.thinkauto.com/

and not really a car specialist, but parts available from many 'service centres' if you know what you want.

http://www.pirtek.co.uk/

IIRC the water connections on the GT25 are done with a banjo fitting M14x1.5 bolts. The oil feed is a banjo M10x1.5, oil return is normal 2 bolt flange.

Martin