A lot depends on when you want to fly. I have generally found very good award availability on UA (and its partner AC). 60K miles round trip to London, and you can also book one-way award flights. It appears you have enough UR points for one R/T and a One-Way...but would have to pay for the return. But, make sure to compare R/T vs. O/W fares...many times they are not that much different and would be a waste to use miles in that case. I don't tend to transfer hotel points to airline programs because the exchange rate is so bad. Best to use the hotel points for hotel stays, in my opinion.

Others may have additional thoughts, input and suggestions.