This website is great for finding pools.
http://www.swimmersguide.com/
I had forgotten about this site. I'm so glad you posted it. I'm traveling over the holidays and found a pool 1 block from where I'm staying.
forums.usms.org/showthread.php
I swam with the Otter group again this past Aug-Sep, and they still allow drop-in swimmers. Here's some examples of their workouts:
forums.usms.org/blog.php
forums.usms.org/blog.php
A lot of the public pools in London are run by GLL Leisure, so you try having a look at their website.
Last week I swam at QMSC (Vauxhall Bridge Rd). It is a good 25 m pool.
