As I said, you can't initiate the checks yourself. You have no choice but to get them done through your prospective employer, unless you are in voluntary work or something and you can get it done through them.
It's up to the registered organisation to set their own charge, though the cost to them is £26 for standard and £44 for enhanced. It's free for volunteers.
Hi you can get your DBS at any employment agency (you dont have to work for them). You will need 3 utility bills, passport and birth cert. It costs between £50 & £70 and takes a couple of days. Wgen you get the hard copy back you must go online within two weeks and register and then you only have to pay once a year a small fee and that way it is up to date by the minute and saves you money. Some employees will only accept a on line DBS. If you are woking in Scotland you will need a PVL.. Hope that helps
You can get a cheaper one by requesting at your local constabulary under the freedom of information act. Its not called a DBS but it has exactly the same information on it. I paid about £10 for one a couple of years ago then last year had to have an enhanced for my job which cost me £44. Only certain jobs allow your employer to check on spent convictions though,