I know someone that has a Merlin and his water pressure varies,if he`s getting 50psi it works well but if it`s only running at 30psi it struggles.£400 for a Merlin is ridiculous are you getting it from ireland with a bolted on pre filter which you don`t need,you can buy them for £220 from different sites on the net but i wouldn`t bother i would get a 40x40 if your in for the WFP long haul.