Now that you have an Elan, the first thing you need to do is find a parts supplier that will give you a personal service. There are many that get recommendations, but for me they are:
SJ Sportscars -
https://www.sjsportscars.comMick Miller -
http://www.mickmillerlotus.comAt SJ, Steve and James between them know pretty well everything you will have a question regarding parts. However Sue Miller at Mick Miller is so helpful and always appears to have time for you regardless of the question or the level of stress she is under, and if she does not know the answer, will get it for you pletty soon. I would try her first...
Your slave cylinder. Do not mess around, for what it is - get a new one.
Rear differential oil, good luck in finding any of those! Use an EP90 transmission oil.
Windscreen seal. You have the Ford Capri type seal. Be careful here as there are a couple of similar seals used on the Ford Consul. My suggestion: Get new seals from Sue Miller above. she knows exactly the one you need.
Painting. Find a good carosserie chap near you. I mean good as the car is GRP and preparation is all important.
Note that as of this week, due to a lot of people losing their way in the UK, brexit has kicked in and all parts that you order will be subject to French VAT that Chronopost or others will collect from you along with a handling fee. Certainly the suppliers above will send parts out free of UK VAT, but if you are ordering elsewhere, remind the supplier to zero rate the VAT and supply copy invoices on the parcel )May sound silly but I have already spoken to two suppliers of other products, one did not know the procedure and the other just did not care and is sending things to the EU with UK VAT making it our problem to claim back the VAT)