Possibly a bit late for this thread but here's my money saving thoughts for a 200+ litre tank stand.
(This assumes you're moderately handy with DIY and have access to tools like a circular saw.)
Find someone who is having a kitchen replaced and grab a free second hand worktop, and possibly a couple of cupboard doors. (Local Facebook groups / Freecycle / Freegle etc)
Use that for the base, top, sides and any internal deviders of your cabinet.
Put something reasonably sturdy on the back, like 12mm exterior ply to make sure it all stays square when you fill the tank. It'll never be seen, so doesn't need to be pretty.
To make the whole thing pretty, clad it in something cheap like 6mm ply. (A 4ft x 8ft sheet is only about £25 and you shouldn't need that much.)
Sand down, slather in several coats of waterproof varnish ... and Robert is your father's brother.
I confess I didn't build this meself, as I didn't have the space to do it at the time, but if I was doing it again, that's what I'd be doing.
(IIRC The cladding is 12mm rather than 6mm, but that gave me thickness tor screwing hinges to the sides, but there are other ways around that.)