Welcome to the fraternity of Bristol Owners, and congrats on your new 407.
I live in New Zealand and have a 411-S1. Like in England, the Chrysler motor is considered an exotic and therefore parts are expensive. In the USA, they are a cheap cult motor popular with a different class of owner than the typical Bristol Owner (no value judgement there, just stating the facts).
Thanks to the internet, you can do mail order world-wide, and when you compare the prices of buying a bolt-on solution versus paying a shop to start working on what may be a worn carb, you may find the bolt-on to be the better option. The key is to go on the experience of other club members, which is what I am giving you here.
On eBay, I found Brandon Bates at Bates Performance in Waco Texas. He remanufactures carbs, but then includes in the price setting them up in his shop (read
the link to see what he offers) to the specifications you provide. I previously had installed a new Carter AFB by Weber out of the box, and several shops in Auckland could never get it to run right. There are many variables in carbs and the cost of a shop fiddling with them, especially when in the UK or NZ, can add up quickly. So I thought I would give Brandon a try. My choice was an Edelbrock 600 CFM 1406 for $200, or a Holley 670 CFM Street Avenger for $250. Chris Browne had better luck with the Holley, so I went with it. The Edelbrock should be a simpler bolt-on, but the Holley is reputed to be the better carb. Both have an electric choke which eliminates the fiddly problems you may be facing.
See
eBay (item 380278510477) for the item. Brandon says he ships world-wide. E-mail is
Batesperformance@cs.com. In my case, I happened to be in the USA at the time, so postage to San Francisco was $25. Before having him post it to England, however, you may want to make a broadcast on this and the other Bristol forum to see if any enthusiast might happen to be travelling to the states and might be willing to bring back some extra luggage. I've done it (both as receiver and courier) and even once had the niece of a forum member pop a 180 kg bronze church bell in a container she was shipping from London to Auckland.
Brandon's price was considerably cheaper than than anything I could find in NZ, and it was a bolt-on fit that ran smoothly without further adjustment.
Things to remember... ask him to include the accessories in the box. With Holley on the big block 383 (you have the small block 318), this includes a spacer to clear the manifold, a dual fuel intake and possibly various linkage adaptor kits, vacuum plugs and spring sets... all a lot cheaper in the USA. For the big block used in the 411, the Holley weighed 15 pounds and the Edelbrock 9 pounds.
Claude