As a follow up on this, I found a gem of a shop in Walthamstow in the end for the front door. It's called The Door Shop. (https://www.google.co.uk/maps/place/The+Door+Shop,+669A+Lea+Bridge+...!4m2!3m1!1s0x48761d8cd3d223c3:0x1e050c79a4304d10?hl=en-gb). Had loads of choice, new and period, and they deliver and install for a bargain price too. Really pleased as I'd been searching for something suitable for ages.
(Ross was good at getting back to me to quote but went the door shop route in the end as it was so cost effective and easy)