For a DSLR, couple of lenses, charger, cleaning kit etc.

Ideally waterproof and with a good level of bash protection.

Bonus points for under £50!

For carrying round with you?

If you are car/canoe/not carrying, then a rigid box one would be best.

I use a second hand lowe alpine soft & padded bag, and a dry bag.

I’ve got an older version of this. It’s pretty good, I’m just a very amateur photographer mind, nice part about it is that you can easily slide it round and get to the camera/lenses without keep taking the pack off. Decent padding and a weather cover. My kit lives in there permanently – DSLR with a stock lens, 70-300 lens, room for another smaller one, spare batteries, charger, filters, etc etc.

As above, if you’re paddling or something then pop it into a dry bag.