Turns out the 3/4" fittings on the Honeywell valve are different to the old Sunvic one, so I can't reuse the old 'nuts' (see pic) and the new valve didn't come with any...
What do you call these 'nuts', and where can I buy some that will fit a honeywell valve with 3/4" connections?
Out of interest, any idea what fitting the old valve is - it appears similar to the 3/4" on the Honeywell valve but is slightly different size or thread so won't mate.
Help much appreciated as I'm rather stuck now...