To update this thread in case anyone else in the UK is looking for a 3 way valve.
I ordered a Jandy Neverlube 3 way valve from a US ebay seller who had reasonable shipping charges to UK.
I ordered an Intermatic valve actuator from a seller on Amazon.com (not amazon.co.uk). Again the shipping charges were reasonable.
I already had a 24 VAC transformer I could use, but these are readily available on ebay as CCTV power supplies.
All now installed and working well.
One issue - UK pool pipe is normally ABS, however the Jandy valve is CPVC. The instructions state to only use "universal" glue and solvent. I couldn't find this anywhere online in the UK, so I ended up taking the risk and using normal cleaner, and normal Weld-On 725 glue. These do NOT say they are compatible with CPVC. However the joints appear solid, and do not leak. I'll update this thread if that changes!