Locking tubs from Walmart or Big Lots are probably your best bet, starter kits are.... Eh.
(Saw you're in the UK/EU looks like so find your local equivalents, sorry.....)
What I'd list for a budget and a new, young snake with a relatively new keeper:
- 32 qt tub with latches ($7)
- 6" plant saucer with hole x2 (hides, cut in hole, sand or lighter hole to smooth edges) ($2)
- stoneware/ceramic water bowl ($4)
- probe thermometer/hydrometer ($15)
- on/off thermostat (very important, do not skip or skimp, this is basic needs) ($25-35)
- uth (make sure to elevate for ventilation) ($15-20)
Means a budget of about $75. Isn't much more than the kit you'd be buying and these are all pieces and setups that will last your snake a good long while. Can move the UTH/thermostat to a new enclosure if its secured with aluminum tape, plastic plant tray hides can be rebought larger as needed, and that tub should last your snake its first year in which time you can secure a permanent adult enclosure ranging from a larger tub to a 30+ gallon tank or a fancier pvc enclosure.
A digital scale with tare and infrared thermometer are also good investments if not already owned.