There are actually a few places to get clean on the way so there’s no excuse to be completely minging. A drop in usual hygiene standards is to be expected though. Namche is a fine place ot get a good shower etc before you go further into the trek where there is little electricity and the temperature drops. YOu’ll prob stay there a couple of nights to acclimatise anyway.
There are many places to recharge your camera batteries. They probably won’t last so long cos of teh low temperatures but you’ll only need to recharge once or twice.
Sigg or similar metal water bottle. Best thing is to get boiled water en route so a Sigg is great rather than using bottled water. Additionally a Camelback bladder and river water with sterilising tabs is good. You’ll run out of suitable streams the higher you go though and depending on time of year they may be frozen.
A trekking pole is a must. You don’t need to spend a fortune on a Leki titanium one though, a simple wooden one will do and you’ll find these in Lukla.
There are shops selling everything you’ll need and more in Thamel (Kathmandu) so don’t go spending a fortune here on stuff you don’t have. The prices are very low (most stuff is knock-off) but the quality is very reasonable. Take a good look at zips, stitching etc but you can generally expect any of the stuff to last the trek with no probs. Take good trekking shoes – don’t save money here. However don’t over-do it either, I generally use lightweight hill running shoes / heavy duty trainers. No need for full on leather ones.
Sunglasses, sun cream, hat with brim, lip balm, skin moisturiser. All a must unless you want to come back all weather beaten.
Emergency foil blanket. LED head torch. Sleeping bag. Layers of clothes are better than big bulky items. Couple of buffs (it can get v dusty walking behind others – use one as a dust mask and one to keep sun off your head / neck).
A book to read on acclimatisation days or journal if you’re into that sort of thing.
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WIFI is available in many cafes in Namche, Lukla and even Tengboche so by all means take a ipod touch, iphone or similar.
Diamox. Know how to use it and understand all the risks with altitude sickness.
Wet-wipes / disinfectent spray. The higher you go, the more and more ill folk you’ll meet. Everyone seems to have a cough or the runs up past Lobuche.
Agree with merino comment. Add some other layers and a thick fleece and you’ll be fine.