Hi Irish
I was in a simeler situation. I completed all of my PPL exams in Ireland under the IAA thinking they would stand when I went to Florida. They did not so I had to sit all 7 of the UK PPL exams.
With the school I was in you had to have all exams passed before you could do your checkride. Maybe this is different for you.
If you don't manage to comlpete the training in the three weeks you could head to the UK. This would be an immense pain in the back side and cost a lot more money. If you can avoid this at all costs. A few extra days in Florida might not be very appealling now but it will take many more months to complete in the UK.
If you get your hands on the PPL confuser and work like crazy at night going over and over the questions you should be alright.
I did complete my training and exams in three weeks but I had covered most of the material when doing my IAA exams.
Best of luck.