At what point to I need to get the chassis number. I would like to stamp it into the chassis before powder coating

Get it when you want during the build as far as I know.

Anytime you like prior to applying for IVA.
Takes about 2 weeks for them to issue it.

I was hoping to stamp my chassis before I get it powder coated, who do I ask for it? I can't find any mention of it on the .gov site

Contact kits and rebuilds department I would guess?address below.

https://www.gov.uk/vehicle-registration/radically-altered-vehicles

http://www.haynesroadster.pwp.blueyonder.co.uk/vinletter.doc


http://www.haynes.co.uk/forums/showpost.php?p=100588&postcount=180


this should get sort you out, i altered the letter a bit as im going for a new reg