Greetings from the T1 Domestic Lounge. There are four showers at the far end of the upper lounge, next to the quioet zone - there is an attendant, and seemed to be full Molton Brown spec (for now).

However, I would recommend hanging out in the T4 Arrivals Lounge as there are (generally) plentiful showers there, but in addition there are services not offered at the T1 Dom Lounge.

You can sometimes get a treatement eg massage, there is a full English Breakfast option (yummy) and you can also get your suit pressed. Arrivals t4 is better than Dom Departures T1. If you are heading over to T1 anyway you could also use the T1 Arrivals Lounge which is less busy and there you would be more likely to snag a massage.