Warp00Doing a little more searching around myself out of curiosity, I found this budget option from Topop for 29 quid including delivery! https://www.amazon.co.uk/dp/B01D641RB2/
Seems the main criticism of them is the cheap keycaps, which wouldn't be an issue in this case of course. Shame they don't seem to be in ISO layout, but the Kailh blues are clones of the Cherry MX blues so this keycap set should fit them fine (although if you're after browns I don't see that as an option on Amazon at least).
There are more budget options around than when I was last looking -- good luck with the search :-)