Can't you buy it from the seller over several months by monthly payments out of the profits it's making? That's a pretty common method, i.e. vendor finance, for tiny businesses.
But as others have said, have you actually checked it's worth that? What are you actually paying for? Is the stock, equipment, etc actually worth that much? Is the stock actually sellable and is the equipment in good condition etc?
It's not good to have to borrow to buy a business as it's never the end of the financial requirements. How are you going to finance buying more stock, or advertising campaigns, or new equipment/vehicle when they break down, or customers who pay late or don't pay at all? Small business is always high risk and you really need a good buffer behind you.
As an alternative, can you not "shoe string" a business, i.e. start your own on a shoe string, get a bit of income from modest beginnings/minimal equipment, and then build it up slowly - far more likely to survive if you do that as you don't have loans to repay on top of earning your own wage to live on, all on top of business costs, etc. Lot of businesses can be set up on much less than £3k, especially "labour only" businesses, so can't you start doing that instead, build up some savings, and then think about buying someone else's business?