Hi Gareth
PM me your address and I will send you the set of rings I have here as they are standard from Japan reseller as Keith said and I required.25 oversize. Only realised when I had the engine stripped.
Agree on the viton seals, mine came from Holland. And your local Honda dealer is a good source, they have access to a Europe wide part search, found an original base gasket in Switzerland.
Keith is a great source of knowledge for the rebuild, great support throughout.
cheers
Stuart