Hello
Lots of places now do dead sea salts via the net for postal delivery, Do a search on google.co.uk for dead sea salt and you'll get a long list and take your pick!
A kilo is about 5 quid....cheaper to buy bulk!
I have bought from findershealth.com in the past and they are a good company. They were also quite local to me and I could pop in and pick them up myself.
I use to run a deep bath and put in a kilo of salt and then lay in it for as long as humanly possible (at least half an hour!). I found that it made my skin very soft and did help the P a little...but I suppose you would need to do this at least three times a week for a good few weeks before it would have any noticable affect...and I never did it that often (time prohibited, as did money! They were very much more expensive when I used to do this).
You can copy the threapy using good old Epsom Salts (and it is cheaper).
I can't say I did it 'seriously', so couldn't say how effective they are for long term use. I did it more as a 'treat'. But I do use The Sanctuary Sea Scrub thing now and then, and it still softens the old P.
SJ