Thanks! seems the best option...I hope there are no big queues...
maybe not the right thread but where to find free showers in London Heatrow T5? (I have a layover of about 10h in London too...) or in London city...I've heard Paddington?
You might want to explore a Diners Club membership - as a credit card it's pretty redundant but at least in the UK the card is now free and comes with access to 400 lounges worldwide (although admittedly not at T5).
There are selected places with free shower or changing room, most of the time in sports ground.
IMO if someone desperately need a bath, public pools can be a good and relative cheap option (well beaches if you don't need hot water :-P). If you stay at a hotel earlier with a Gym facility you can ask if you can come back for a shower later (no guarantee success of course)
OR .... ask for trial membership at those private gym club (I think Pure Fitness offer trial membership for HSBC Card Holder .... ), but then it is last resort and way too complicated....
Public toilets and shower places in HK are never that dirty, but always moist and wet, since few if any are air-conditioned. Wet floor, wet seats, wet walls. They are not someplace most will want to shower unless absolutely necessary.
The large public toilets that likely have shower stalls are those attached to wet food markets, and if you've been to one of the markets in HK, you can imagine what the toilets and showers are like.