This will be an opinion splitter but essentially you have a couple of options. Cheap tool cabs, budget tool cabs, 'pro' range cabs and Snap-On.
Cheap tool cabinets:
Don't buy cheap ones. They'll fall apart and you'll have to replace it. The drawers bend and can't take any weight and it'll generally annoy you.
Budget tool cabinets:
These are I'd say you would get if you paid a total of £250 for the top and bottom cab. It's the middle-range (red) Clarke and Halfords 'Pro' kit. They're fine for in the garage, but if you have to move them around the wheels show their limitations, the cabinets get bashed up and dented easily and they will start to look tatty. If you think you'll need to move them around (e.g. if you were a contractor and work from place to place) then you will need professional quality cabinets...
'Pro' range cabinets:
Tend to be made out of much thicker metal, the drawers are considerably stronger and latch and lock closed properly, paint finish is a lot thicker and the cabinet itself has shaped sides for extra rigidity. Usually a lot heavier and the bases are stronger with much better wheels. They are designed to be rolled around and can take being bashed about without getting damaged. Typically these are the blue Clarke range (which I've got), Teng, and will cost £400-£500 for a top and bottom cabinet. If you can stretch to this, I'd recommend them because they will be the only tool cabinet you'll ever buy, i.e. you'll never have to replace it.
Snap-On:
Considerably more expensive. Quality is very good but you need to be able to justify the extra price or want to use their finance and guarantee for your set of tools. You get the added bonus of them (technically) replacing anything that breaks and coming to you rather than you having to go to them.
Machine Mart is a good place to go and look because they have cheap, budget and 'pro' boxes you can look at and play with. Then take a visit to a Halfords where you can see one of their black 'Pro' range cabs as a comparison. You probably don't need a bottom cabinet (a roll cab) but a decent top box will set you back about £150 in my opinion and you'll never have to replace it.