Art finance is a very specialist part of the market, and few lenders operate in the space.
Because of the process and risks for lenders (i.e., art needs to be valued and appraised and the fact that there is always a potential risk of theft or damage), most lenders will only consider lending amounts of £2 million or more. Given lenders will only let you borrow in the region of 40% of the value of your art, your piece or collection needs to be significant for this type of financing to make sense.