I will be shopping in France but I have a 5 hour layover in London (LHR). I understand that VAT forms need to be completed in the last EU country you are departing from, so in my case at LHR. Do I have the option to detax in France since it's only a layover in LHR?
I have read that the detax process in LHR is different than in France and Italy where I normally depart.
Yes, you can detax in France. I recently traveled from Naples to the US via CDG and detaxed in Naples. I would recommend you detax in France since your flight could be delayed and it can be confusing (at least to me) to find the detax while you are connecting