My RHF caliper has started dragging, and I am not prepared to mess around with seals etc, the M16 is easily powerful enough for me, so what are the alternatives/good sources of replacements

big red on ebay can do replacements it is easy to do your own I bought a new set of pistons and seals for around £70. you could always go the hi spec route but will be £200 plus

Any motor factors will do you refurbs on exchange.

saves on the postage to big-red.

Motorfactor refurbs will only be about £60-70 a piece exchange.

Even people like halfords usually charge the same as a 'proper' motorfactors for exchange calipers.

Don't Wilwood do a direct replacement? Rally Design do recon ones

I've got Raceleda R16... brilliant.
I've already used big red in the past - with success

I have just changed both fronts for £66+vat the pair, working great.

Local factor got them within 24h, and a £10 surcharge each.