OK - these cars may depreciate less - maybe even gain a few pounds in value. I've now owned two F cars and neither have cost me a penny (outside of tyres, brakes etc). Running and servicing a Ferrari - different ball game. No way could you use it like you can an F and expect no issues! Even something like an NSX (which has got an amazing reliability record) could end up costing you large!
NSX - lovely car, and I would consider having one. This one however is an auto. Bottom of the collector's list.
Finally, as for buying cars cash..... why not? You know where you are and you don't pay interest. If you've already got ample investments in other areas and don't need free cash set aside, then why not buy a car cash?
Edit: Depreciation wise, many RC-Fs have already shed £s. a £65k car for £30k - not bad really is it. For that, you have a bullet proof NA V8, with traffic stopping looks and a modern cabin.