Unfortunately I know Gatwick better than Heathrow so I cannot offer specifics on the spa idea. Gatwick has a Clarins shop which offers excellent facials, massages and other spa treatments. They have several private treatment rooms. Hope something similar turns up at Heathrow, Cosmo.

Thanks cmsfong. Did a search last night and found as you said lots mentioned in this regard for Gatwick but not Heathrow. (does say beauty - but no link or specifics) Ill just have to check it out on the day.
Thanks also Flanneruk for your great response. That Little Venice canal work sounds enticing.. might check out the logistics and see if it all "seems to much" or give it a go... and then there always the shops... (Im actually not good at shopping - sad really, find it all too hard)hee
thanks again

Some airlines sell day passes to their lounges if you are an elite FF or if you indicate you want to try before you buy. Every lounge in an International terminal that I've been in has a shower and some kind of Internet access.