Thanks all, again - really appreciate the comments.
Thanks for this Joe. Considering this as a destination for next summer (with Emma). Not sure I like the sound of the hostels (I like my sleep!) Do you reckon it would still be doable to base ourselves in one of the main towns and do day walks?
I think the hostels would be fine on a weekday out of season, as it was, our two mad nights were the Friday and Saturday nights. The Morskie Oko and Roztoka hostels on the Sunday, Monday and Tuesday nights were tranquil.
The town of Zakopane would make a decent base. You could get up Giewont, or anywhere on the Kondracka Kopa - Kasprowy Wierch ridge in a day. A 30 minute bus ride takes you from Zakopane to Polana Polenica (where we finished our trek) where you can get the horse bus (or 10k hike) up to Morskie Oko. There's plenty more of the Park to the west of where we were that we didn't get near. If you went to Slovakia, you'd have about 4x the area to explore. Cross border walking is allowed, so you could take in part of both countries.