Keep in touch with fellow enthusiasts.
https://www.facebook.com/rapidmechanicalservicesltd - Rapid Mechanical Services. Andy was really helpful at getting rare parts
https://www.deroure.com/ - probably the best resource we have for identifying which parts you need for a bit of work. Whether you order from them or not is up to you, it's just standard Lotus parts prices so nothing to shout home about, but in terms of figuring out what you need and whether it's readily available it's unbeatable!
https://www.sjsportscars.com/ are a useful resource too, particularly for S1 parts. They hold quite a lot in stock and also have 'Steve's Alternative' non-OEM options. Basically anything they have a photo of tends to be in stock, which from experience is better than waiting for 'factory order' from Lotus which could be anything from next day to next year