Never pay up front whatever the country or school. Why should you? It's usually a sign that a school needs cash quickly when they offer discounts. Pay by the hour even if it is a few $$ or ££ more. Offer to settle all flying charges at the end of each day flown.
The cost of training in the UK is way more than in US. look at approx £300 an hour. But as you rightly say, once you add in cost of flights to and from usa, accomodation, socialising, eating, transport whilst there etc, the difference isnt that great. You may fly every day and never see a cloud. Ive seen guys come back from usa having done all of their certificates, and the school I worked at in the UK had a couple of USA trained guys come to use the helicopters SFH, HoT having given them the check ride to hire the aircraft, they wouldnt allow them to fly, as their standards weren't up to it, nor were they prepared for the weather difference. Im not saying thats a generalisation, but its possible and ive witnessed it.
Similarly, I have seen the US IR trained pilots come back and struggle to do a basic IR flight in the sim. Maybe they were just not very good, who knows.
Overall, I ended up trying both routes and found it was going to be more beneficial for me to fly and train just in the UK, but that was after I had gone out to Florida with a new PPL in my hand, and did some SFH for a couple of weeks hour building in the sunshine. Nice change from 30kt winds and snow.
