Having spent time in both Swanley and Overwater, I would say it depends what you want out of your mooring. The Star at Acton is indeed a short drive away and certainly used to be a cracking pub. However, if you fancy a few, it's not a nice walk back on a dark country road and we never managed to find a taxi. That was the biggest decider for my old man when he moved down to Overwater - quick walk down the towpath to a choice of three pubs, co-op, chippy, post office etc etc etc.
Yep, Dominic may have a vested interest in the marina, but I don't, and it is run by lovely people. As an example - my dad posted on faceache last night that he'd run out of gas - within minutes he'd been offered a spare bottle of gas, camping stove and kettle and any other help he might need from other moorers. On arrival at the office this morning, he was helped to move the gas, and a hot drink made for him while he waited.
If I was in the area and wanted a marina mooring, I know which I'd pick