auchencrow

I would not be so quick to write off that frame - or to repaint it.
Yes there's rust but I've seen others in that condition come back remarkably well.
What it needs is a good oxalic acid bath (AKA "wood bleach" available at paint supply stores) followed up with a liberal application of Meguiar's Scratch-X and polish.
The inside of the frame should be treated with frame saver or "Boeshield T-9" - this leaves a waxy coating inside to prevent further rust.

The stem & etc should likewise benefit from the OA treatment -(there are many threads dealing with it here). It does especially well with chrome but does not like zinc or aluminum alloy.

You wheel rim does not look like a Westrick pattern to me. I am not sure that it is original. There are EA3 replacement wheel rims available, and though you say you don't care to fiddle with spokes you may have to - - rust is especially unkind to spokes, unless they're stainless steel.

Depending on how well the fenders clean up, you'll have to make a decision - to repaint or keep them as is or replace them (Raleigh fenders are common enough).
(The fenders on my later '53 Sports looked like yours but I am pretty happy with them now.) Anyway, bondo is not going to work out.

For rusted screws I'd recommend PB Blaster - It's a penetrating oil that works well with rusted fasteners. Be advised that these are mostly 26tpi proprietary-threaded fasteners that are not easy to find.

For replacement parts, such as the chain case closure, eBay is your best bet. Another alternative is a parts bike, if you can find one. If you are where I think you are (in Merry Old England) this might not be such a daunting task as it would be here.