It matters which end of the train you're at. 240m is a fair way to walk. For the below, when I say the end of the train, I mean the very end if you use the lift, 2 cars in from the end if you want the escalator.
At Bond Street, if you want to change to the tube, be at the West end of the train. There's an intermediate-level tunnel with a bit of a walk to the tube station; the Lizard Line (love that) is one block South of Oxford Street while the tube station is on the North side. The East end is nearly as close to Oxford Circus if you want the Vic/Bakerloo. It counts as an interchange so you won't get charged extra.
At TCR, be at the East end for the tube.
At Farringdon, if you want the tube or Thameslink, be at the West end of the train. It's no walk at all. You emerge at the Thameslink station and have to cross the road outside to get to the circle line (or you could go via the Thameslink platforms and overbridge inside the station). The East end is just round the corner from Barbican station. There is technically a link to Barbican station, but it's only a lift to the Eastbound circle line platform so pretty useless.
Be at the west end of the train to exit at Moorgate, and at the East for Liverpool Street. At both ends, changing to the tube means going all the way up and all the way back down again; no intermediate-level tunnels.
For completeness, at Paddington if you want Bakerloo be at the mid-West of the train. There's escallators down from the Lizard Line platforms. For circle line, you have to go all the way up and then through the main station. Marginally quicker to be at the East end of the train for this. There should have been a direct tunnel from the concourse level but it was removed to cut costs.