A laptop might be able to do it, for rather more than that budget. A tablet is pretty much out of the question. A custom, self-built desktop could, probably, squeeze that much performance out of Toribash, but it wouldn't be great by any means. The 320gbp tier listed on that site in the sticky would probably be able to get everything besides real-time raytracing, so yes, it should be doable.
Just, if you want to build a computer for gaming purposes, it'd be worth it to expand your budget a teeny bit if at all possible, especially since, aside from RTRT, Toribash isn't particularly demanding and doesn't have particularly demanding features. RTRT actually isn't that terrible for a graphics card either, so long as the GPU has proper double precision support, and you don't have more than about 100-120 objects being rendered at a time, considering the standard 80-ish objects for Tori and Uke.
Last edited by suomynona; Dec 20, 2013 at 05:18 AM.
Reason: Slightly edited for clarity.