Spanish bank Santander is reportedly planning a listing of its UK operations on the London Stock Exchange in move that could raise up to £3bn.The Financial Times says the lender could list on the main market as soon as this autumn to fund further expansion.Santander is planning to float around 20% of its UK business, which includes Abbey, Alliance & Leicester and the savings arm of Bradford & Bingley, the paper reports, citing people close to the bank.The group, which confirmed last month that it has entered a bid for about 300 high street branches being sold by the Royal Bank of Scotland, needs the money to fund that deal, the FT adds.Market speculation suggests Royal Bank of Scotland's branches could be worth about £1.8bn. Santander is rumoured to be the only bidder.A deal for RBS's old Williams & Glynn businesses would make Santander a major player in the UK bank market with 14% of the mortgage market and 10% of retail savings. The group is keen to expand outside of its core Spanish market, which has collapsed due to the fall-out of the credit crunch and a property market melt-down. Most recently it bought 173 branches in Germany from Sweden's SEB for €555m.