Well, we have arrived to London in one piece! We did have an interesting experience in customs after landing as we wrote on the custom forms we were going to be in the country for 61 days.  The customs officer was nice, but very thorough in his questioning and wanted to see proof we were not planning to stay in the country longer.   He asked to see our flight information from London to Portugal, which I could not locate on my phone, so instead showed him our rental car reservation and all our Airbnb confirmations in Portugal.  This seemed to satisfy him as he stamped our passports and we were free to collect our bags.