Considering change of plans

I wouldn't stay in St Ives- I would stay almost anywhere else in Cornwall but St Ives. It is a lovely town, don't get me wrong, but gets seriously over run with tourists. The streets are very narrow and congested- so much so that day visitors have to park up on a hill out of town, and bus down the hill. If you book a place there you may be lucky enough to get a parking place.
Maybe consider Penzance or Falmouth, or the County town of Truro as alternatives? If you are wanting the Penwith peninsula (which St Ives is on) then what about St Just?
If Exeter is just to pick up/drop the car (and that is doing the City an injustice- it and down to Exmouth, the coast beyond and the inland towns of Axminster and Honiton are worthy of your time) what about train down to Truro, and rent the car from the rental agency on the railway station?

I think that sounds very do-able, giving you 4 days and 2 half-days in Cornwall, more would be great but I think that’s enough to give you a good taste. You’ve been sensible in avoiding the long drives from Bath and London by choosing the train, and as long as you’re happy driving on some narrow lanes in Caornwall, you should be fine. Google maps was great for me a few years ago. The weather could be anything from pleasant to wet, but that’s island weather in October.

isn, thanks for those ideas, I will investigate.

amanda, Thank you... i get it about the weather.. We live on the peninsula of Florida so we get a little of that changing weather. Not quite as much as an island.

I agree with isn31c that St. Ives is very touristy. I spent two full days in the area, exploring galleries and wandering around the shops. St. Ives has a train station, so there's an option to train in from a different place.

If you like gardens, I recommend both The Lost Gardens of Heligan and The Eden Project on the other side of the peninsula.

Due to a lack of last-minute summer hotel rooms on the coast (duh), I also spent a night in Exeter and a night in Truro. I liked them both. They felt like places folks lived rather than beach destinations. I wasn't driving, so I have no idea about a convenient location for a traveler with a car.

You might want to use ViaMichelin to get some driving-time estimates so you don't bite off more than you can chew. You'll probably be driving more miles than expected, due to the layout of the roads (not hugging the indented coastline), and you'll be covering ground rather slowly.

I have a different opinion on St Ives. Yes it’s popular and full of tourists but there is a reason for that. It’s absolutely stunning. There’s something really special about the place. The light has drawn artists for years and you can really tell that the light IS different there. Once you’re in St Ives you can park your car and explore on foot or by train.

I'm with isn31c on this one - St Just is delightful and there is some superb walking from there along the coastal path.

Last fall I rented a car in Exeter for a loop through Devon (Dartmoor park and some small towns north of it for family history) and Cornwall. It worked out nicely as Exeter is a gateway to Devon and Cornwall.
But If you are only planning on seeing Cornwall, it might be more quicker and more efficient to train it past Exeter to someplace closer to or in Cornwall. Maybe Bodmin or Penzance and do a loop around Cornwall.
As is always the case I was rushed for time, and after the Penwith Peninsula I wanted to see St.Ives but decided to skip it after reading Rick Steves comment about parking in his England book. With more time I would have put up with the extra hassle, but was feeling rushed so it was kind of the excuse I needed.
Pasting from Rick’s England ebook, hopefully this works:

“By Car: St. Ives is a pain for drivers—parking is scarce and distant from town, and those who venture into the center find its streets congested with slow-moving pedestrians. As you approach town, you’ll reach a roundabout with a “do not enter” sign (9:30-16:00, except for permitted vehicles). While this isn’t usually enforced, driving past here is challenging enough that you’ll probably prefer to park at one of the outlying pay lots (all with similar prices). The main option is the huge Trenwith car park above town, near the Leisure Centre—“

Rick misses out the best way to visit St Ives by car. That's to park at St Erth railway station and take the train down the short branch line. It allows you to ride the short but beautiful train and delivers you right into the centre of town. Driving up to the car park will provide some extra stress and leave you with a long walk uphill back to your car when you're done.

Thank you Greg and John,, That is valuable info about taking the train into the town. I will be sure and print this for my folder.... i wish we had a like button for posts.

Last time I went to St Ives for a few days I parked at the rugby club which is £7 for 24 hours. It’s a bit of a walk back uphill to get your car, but you don’t need to use it at all when you’re there so just park and forget.