I'll leave a few notes about dealing with the modern-made Westwood rims available online. I've dealt with quite a few types, but not all of them. My experience from best to worst:
-original rims - Raleigh; Phillips; Hercules; Dunlop. By far the best. They tend to be heavy but have a long lifespan. The best of these are the "stainless" ones made by Raleigh after WWII in the 1950s and into the early 1960s.
-bought from Yellow Jersey in Wisconsin (call/email direct) - Yellow Jersey in Wisconsin developed a cottage industry of working with rod brake roadsters and spare parts. They've stocked several different brands over the years from what I can tell. They formerly had "Eastman" rims and spare parts, which I would describe as fairly decent parts. They're not as nice as original British parts, but they're pretty good. The same seems to be true of KW brand rims. They're not as nice as originals, but these are not bad. I've used both brands and they do OK. Yellow Jersey is very good about answering questions.
-bought from online/eBay sellers in Britain - the worst rims and parts I've bought have largely come from British sellers. I've gotten rims branded "Avro" and rims with no branding on them at all. The Avro rims were mediocre: not as nice as the KW or the Eastman from Yellow Jersey. The no-name brand ones were really wimpy. The sellers are not as helpful as Yellow Jersey if you have questions. But they do generally fit and are an option if you have no other alternatives. It gets expensive to ship these. Other parts from these sources have also not been very good - handlebars; brake parts; etc. The parts may be coming from Pakistan or China - they seem different from the Indian parts I've seen.
The one I have not yet tried are the parts from the German "Classic Bike" or "Classic Velo" site. Supposedly they have both steel and aluminum alloy Westwoods, but usually in 36 hole rather than 32 and 40. The alloy interests me because it may be an option for bikes where you want to improve the performance. But the shipping and cost of getting this stuff here has been too high for me to try it.
You have to have nipple/eyelet washers on the Westwood rims. I've seen people get away without them on the original rims, but it's not a great idea. Don't try it on the new India/Paskistan/China rims - the eyelet will bulge on the rim. The no-name brand rims even bulged with the washer and normal spoke tension. I'm not touching those again. Look for "Zipp Firecrest" washers.