hi
the best place i would suggest is a beauty supplier. where do you live? i use Sallys Salon Services, they have branches throughout and are open to both trade and public.
you would have to buy a heater to melt the wax in. i'm a beauty therapist and I use my normal wax pot for both waxing and paraffin wax. you can buy different inserts for them.
if you do get a heater be careful. don't put your mothers hands in when the wax is still clear as this will burn her. wait till it cools and is cloudy then dip it in, also get a paraffin wax brush. you would dip her hand in, pull it out. wait 10-20 seconds and dip in again, then wait then do it once more then wrap the hand in cling film and a towel. you can buy heated mitts but i find that cling film does the job.
if you don't have a local salon services, argos sell the large heater and you can buy the wax blocks or pellets from any salon supplier. the last time i got 1kg of tea tree pellets for �5.50.
Here's some links to check out:
http://www.argos.co.uk/webapp/wcs/stores/servl et/Search?storeId=10001&catalogId=1500001001&l angId=-1&searchTerms=PARAFFIN
http://www.beautyexpress.co.uk/find.asp
http://www.salon-services.com/
http://www.hive-online.com/v3/maincat.asp?cati d=2&catname=Paraffinalia%20by%20hive