In reply to AlanLittle:
The Centurion looks fine - better components than the Decathlon and has the advantage of having air forks - suspension is adjusted by pumping in or letting out air. This gives much better tuning than sprung forks which are adjusted by tension on a steel spring.
Another advantage is that you can try it for size. Mountain bike sizing is erratic so it's always best to try several sizes. Current vogue is for long top tubes and short stems (traditionally frames were relatively short, sized by clearance between crotch and top tube, with stem length being used to get the right reach.)