5-8 Day tours of Cornwall recommendations

Rabbies which gets consistently good reviews on here do a couple that might suit you.

This 5 day tour starting from London or this 4 day tour starting from Bristol.

We did the Rabbies tour of Devon and Cornwall and it was fantastic. Our guide was wonderful.
Also, the price of the tour was very low. You can book your own lodging or Rabbies will book it for you. You pay direct to the B&B or hotel.
Rabbies picks you up for the touring.

Not sure if this would be too long to meet your needs but Road Scholar has a 9-day tour that I see now starts in Salisbury and ends back in London. It stays the 1st tour night in Salisbury and then most nights in Falmouth with day trips, then ends back at Heathrow for 1 nights. The RS tours count the day you leave the US as Day 1 so it shows as a 10 day tour but it actually meets up on Day 2, so 9 days (including the final day which is not really a tour day either!).

Also, not sure of your age ranges and if you are interested in a tour aimed at the senior market. They say the go down to 55 but most participants are 62+.

https://www.roadscholar.org/find-an-adventure/22431/Cornwall-England-s-Hidden-Treasure

I did this one in October 2019 and they've changed it a little with the start in Salisbury. That is a very easy location to get to from London and in fact if time allows would be a great place to spend a couple of nights ahead of the tour start. The tour was wonderful. We were in a 15 person van so could get down some of the narrow lanes in Cornwall that are not accessible to buses. The leader and local expert were wonderful and I learned a lot and saw a lot!

The change of the tour start is a plus as the ride on the bus from London to Falmouth was pretty long.

Be sure to compare PRICES of tours. Yes, Road Scholar is excellent, but I am sure MORE expensive.