There are 3 trains per day Monday to Saturday and 2 on Sundays from Clapham Junction to Bath. Takes 2hours 20minutes but is much cheaper than going via Paddington if you ask for a 'via Salisbury' ticket. Even cheaper if you have a Goldcard or Network Card if you split your tickets and buy Denmark Hill - Salisbury, and Salisbury - Bath. Alternatively if you don't mind also changing at Salisbury the SWT trains run hourly Clapham Junction to Salisbury, with FGW connecting hourly Salisbury to Bath. The ELL extension to Clapham Junction makes it a lot easier to get from Peckham Rye and Denmark Hill to all sorts of exotic destinations ... Exeter, Southampton, Portsmouth, Reading, Milton Keynes, Watford etc.