Aye! Something that's 2x and also loud is 2x810! Ideal for you!
Seriously though, it all depends on the type of sound you're after. I would normally choose the cabs I want, and then find the amp that will drive them, but this is me being not a bassist.
The F1 is somewhat neutral, unlike MarkBass's own cabs. I like the MarkBass cabs, but many do not. 250 quid should enable you to land a second hand MarkBass 102P which IMS is quite a punchy little feller.
Genz Benz must be mentioned again, as their last cabs go for peanuts at GAK and Bass Direct.
Other than that, if you tell us something about what type of sound you're after, or what types of music you play and where you play it, it will be easier to come up with ideas about a £250 cab. For that amount you could get a relatively loud cab of simple pedigree, or less noise of higher quality, so some narrowing down is required.
On the one hand you have these old fashioned, lazy speakers with limited bandwidth. On the other hand you have those that aspire a near perfect representation of the original signal. Unscientifically, I tend to divide sound ideals in Old Skool (like Ampeg SVT), Hi-Fi (like Vanderkley) and Signature (like Gallien Krueger), but more experience people on here will probably think differently.