Well the UK get there enriched fuel from the US anyway for the sub.
Good article here if interested about nuclear subs and ships and who uses what type of power plant - Nuclear-Powered Ships* Rolls-Royce claims that the Core H PWR2 has six times the (undisclosed) power of its original PWR1 and runs four times as long. The Core H is Rolls-Royce's sixth-generation submarine reactor core.
The PWR3 for the Vanguard replacement Dreadnought-class SSBNs will be largely a US design – presumably based on S9G in the Virginia-class – but using UK technology. It will be more expensive to build but cheaper to maintain than the PWR2. All UK submarine reactors use highly-enriched fuel, obtained from the USA.
