I think we'll see $1.15 : £1 soon enough, so personally I'm waiting but that's only a £100 difference on what you're changing. Presumably you'll make money on the conversion now anyway (assuming you flipped to USD before the most recent fall), so could just transfer now and forget about it. Whatever you do avoid the airport currency shops as their rates are abysmal, your own high st bank will probably be better, but your best option is one of the currency brokers (e.g. transferwise, currencies direct, UKForex) which all give much closer to the spot rate, but you'll need a USD account to send them the dollars from though.
Trump victory may have an immediate negative effect on the dollar but then will come Brexit knocking the pound down again, also likelihood of Trump now is small.