The price will vary from day to day but at the moment they don't seem to jump/drop too much, upto date pricing is
here You can buy them through most banks after setting up a share trading account, many here have used Halifax. You also have to factor in a fee when buying them this varies from bank to bank.
You need to buy a minimum of 5 to join the club & pay a 30 fee every 2 years or 20+ shares will have the fee waivered for the membership but you still need to renew every 2 years.
Benefits to joining can be found
here