It is very difficult to compare apples with apples on this one.
OK, you have accommodation and food costs with US based training, but do you eat free in the UK? Remember that Wal*Mart is cheaper than Asda!
What are your travel costs to/from the UK airfield? US schools usually have accommodation near the school.
A PPL course typically has about 100 landings/touch'n'gos which are usually free in the US but usually £5 - £15 each in the UK
Will the UK club require a membership fee (£100 - £200 common) and/or payment for a security pass?
How much will the school (UK or US) charge for each ground school exam? For the radio practical? The examiner's fee for the skill test?
What will be the total cost of Visa, SEVIS, TSA, fingerprints, travel costs to US embassy/consulate?
The OP included in his budget 1000GBP for JAA medical, headset, textbooks etc. These will all be required if training in the UK, but will be cheaper if obtained in the US (yes, a JAA Class2 in the US can cost less than many UK AMEs charge).
And there's PROB90 lots more that I cant think of! And of course after you get your costings down to the last penny and cent, the exchange rate will change.