In the pool! Finally I managed it, I wasn't sure when I set off but got to 40 lengths and thought I'd just carry on. It's been a huge milestone I've wanted to achieve but it's always been too busy, or more commonly blooming cramp has set in but all the planets were aligned for me tonight and I managed it. Slowly but steady... Just like the tortoise!
Thanks -,just had to write this down for posterity - so excited!