Hiya Roy,
Welcome to our 400th member on the site!
Best of luck to you on your second attempt. The guys from St Vincent (As you're probably aware the RN has had two recruiting drives over there in the last 5 years) probably found the most difficult thing, apart from fitness preparation, was trying to get used to the climate change & some of them suffered cold-weather associated injuries on Recruit Training.
Obviously there's no easy solution for preparation other than perhaps allowing some time to acclimatise in UK if that is feasable & possibly trying to start Recruit Training in the UK Summer in the hope that you gradually get used to the cooler weather.
Again, good to see you on the site!