What do people recommend? Getting rid of carpet is not an option unfortunately.

shower curtain – about £4 B&Q etc etc etc

Interesting, that hadn't even crossed my mind.

When at work we use a self adhesive carpet protector, it's ok to leave down for up to a month, removes easily and stops the customers falling down the stairs, google for "self adhesive carpet protector"

Rubber car mats

That carpet protector looks good. I'm thinking a layer of that under a cheap rug might be a nice solution.

It does work well, only problem we've ever had is that is leaves the customers carpet really clean when we take it up. 😆 Makes the rest of it look awful. Shorter rolls used to be available from wickes, B&Q and Screwfix if you've got any of those close by.

Cool. Just need something for the wall now where my stairs curve around. I presume the carpet stuff could take paint off if not removed very carefully.

Ooh yeah, wouldn't recommend it for the wall. Probably need more detail here but how about taping some interlocking laminate flooring to the wall, use clear packing tape and you wouldn't see it much, well a little bit sort of. 🙄

I'm thinking something like this might do it: http://www.magicwhiteboard.co.uk/

Used to stand mine in a length of plastic rain gutter with push-on end caps.