Dont all Training PPL's get to fly solo as part of the licence requirement.
As you did your training in the US I am guessing it was under FAA and not JAR, so as you never completed you have no licence to convert.
I am assuming you want to do your licence in the UK under JAR, and therefor you are going to have to start from scratch.
Check the FAA route, FAA might except the hours, and therefore you could get an FAA PPL in lets say 20-30 hours, then convert it to UK.
If I were you I would start from scratch, the extra hours could be used to hone CPL and IR skills