It's a good question in regards to value.
Napkin math would be good condition MSRP minus cost of all the parts needed to make it "good" again, minus downtime and labor needed to get it back to that position with another minor minus in value for the gremlins that are still unknown.
With that said values to begin with have been all over the place with even 2000my Zetecs fetching around $40k on BAT in great condition and desired spec.
Caterhams in general in any spec and condition tend to go above $20k and some other 7s slightly below that as bottom and completed Locost replicas in low to mid teens. Low volume means they are always in demand.
Throwing another wild stick at it, as is it's value is likely about $20-25k barring no major mechanical, title or frame issues. As long as the frame isn't rotted through and the engine at least turns by hand and it has a title that would be a very good start.
Once it runs, you clean it up, replace or paint the fenders (Carbon would be a good "resto mod" for modern look) and have it moving and sorted you're into $30s depending on true miles and rest of blemishes. For personal use I'd recommend sourcing 10 spoke 15in wheels or even 13s. I believe yours now are 16s? Maybe 15s?
My opinion of course. Many much more seasoned vets here that will chime in with their knowledge.