It has been a while since I last looked up the prices of seat boxes and am more than a little surprised having now done so.
Before checking I'd have thought there was a lot of choice around £200 but . . . seemingly there is not.
Under the £50 price you have the Diawa or Shakespeare plastic boxes which while very basic are nonetheless good value but do not have leg levelling devices . . . . .
Then there is a leap up to £149 for the Daiwa 50 seat box or £179 for the Maver signature.
At this price you get telescopic feet so making for simple levelling and a mixture of side and front drawers although they look more suited for pole fishing in all honesty.
There may well be others on the market but that was the total of my search, and to be honest I was rather disappointed.
In that price range I think I would be tempted to look at the second hand market as there must be better options available. Personally I'd be looing at the Preston range as all their accessories will fit their boxes and the quality Iisvery good, even second hand.
PS: just took a look on E Bay and this one looked good to me as it is the same seat box that I have:
Fishing seat box | eBay