I noticed they advertise a welcome package that spreads across your first five deposits instead of just giving you a one-time bonus. How does that breakdown actually work in practice, and is it worth claiming all five stages?

It’s set up to give you huge percentage boosts right at the start, though the match percentage scales down as you progress through the package. If you check out the full breakdown on https://magicwin.me.uk/, it kicks off with a massive 400% match on your first deposit plus free spins, then steps down to 200%, 150%, and finally 100% on the remaining top-ups. The main draw is the sheer size of the bonus balance you get to play with early on, though you need to keep an eye on the 50x wagering requirement attached to each stage before you can request a withdrawal.

Definitely check the wagering requirements and eligible games before activating each stage in the cashier. Since each tier triggers separately upon deposit, you don't have to commit to all five stages if you feel like playing through just the high-percentage first tier.