Hi Bruce,
Judging from the lack of response I guess nobody else knows either, and I can only add an opinion rather than real life facts to help your decision.
Hubs first. I think I mentioned a while back that I'd used aluminium front hubs on a Marcos I once owned (Triumph front suspension) to get Ford PCD to match the Ford rear axle. They looked identical to the ones Canley sell and have been around the Kit Car scene in the UK for many years now. I had no problems at all with the conversion. A point to watch is the bearings because the GT6 has a thicker stub axle than the Herald, Spitfire and Europa, and also larger bearings. So if you buy a hub for the GT6 then you'll need the axle & bearings as well.
Looking at their website I see they do an "uprated hub" kit where they machine a new axle & hub to accept larger bearings. Personally I'm not convinced larger bearings are needed, but that's the sort of parts shopping list you'll need. And of course if you want to change PCD then an alloy front hub is the best way to do it IMO, tried & tested.
As an aside, if you go to Ford PCD at the front, how are you doing the rear ? Disc conversion & new hubs there as well ?
Brakes. The calipers look remarkably like the AP Racing ones fitted to my S1 Elise, and they take the same brake pads but the discs themselves are different and the outer castings have "Lotus" on them. But the basic design looks the same.
I'd have no concerns about the components per se, my only thoughts are about what it will do to the brake balance across the car. The standard calipers can easily lock both front wheels and if you are a regular on the Yahoo list you'll know all about the regular debates about brakes and rear disc conversions, so increasing the front stopping power will certainly upset the balance if done alone.
If my guess about the calipers being similar to the Elise ones, then that car is a touch heavier than the Europa, has 185 & 205 tyres and has the same sized vented discs all round. The brakes are superb and feel better than the stock Europa, but it's a complete system design. I think you'd have to do a similar thing.
Brian