How to protect deposit?

[pinkpedi]

I'm having some work done in my house, booked in for mid Jan.
the builder has requested £1k deposit bank transfer and then 3k in cash first week and second week and then rest on completion. The job will take 3 wks.
mostly sounds reasonable apart from ...
how do I know he won't run off with my deposit? I don't want to annoy him but so many builders just ghost nowadays... he is the 7th one I've contacted. He was a recommendation but person who recommended him initially hired him through a design company.
Also cash payments, that sounds annoying and will be difficult to arrange. Not to mention probably tax dodging!

Thank you so much everyone, I've just seen all your comments as at work today and it's difficult to reply to all.
I hear what you are all saying, and yes, I agree not everyone is vat registered I have my own business too and try to keep my prices as low as I can to keep my clients and to avoid the whole stress with vat. But to ask for cash does sound dodgy to me and on his official quote it should have had a vat number number on it if that was the case surely.
I've told him I'll happily send over the deposit immediately but want an invoice first and that I'd like to stick with the agreed price and pay by transfer. That I would also like to see a public liability certificate and I asked if he would give a 12 month guarantee for workmanship.
now expecting him to ghost me! I hope not because even with 20% added it's still a reasonable quote.
It will be very annoying but as others said I can use all my fixtures when I find someone else... if I ever do!

realistically you cannot "protect" your deposit unless the builder enters into a legal escrow account - which of course defeats the object since the builder needs the money up front to buy the materials for the job.

Get the builder to order in your name and get the materials delivered to your site, Then you own what you paid for and if the builder "disappears" then at least you have the items you paid for.
Downside is it might cost you a bit more £ as the order will not necessary get the builder's trade price rate...