Base at Brixham/ Torquay and
1) Go west Dartmouth, Salcombe, Newton Ferrers Plymouth and even into Cornwall
2) Go Noth & East - rivers Teign & Exe, Lyme Regis, even Waeymouth - stunng coastline.
I guess the questoins are:
1) Day trips or a anumber of days for a single trip, stopping over at night?
2) How big a RIB?
3) What length of trip are you comfortable with in a day? -no doubt dependent to an extent on RIB size
Consider the weather if you're coming over in October - autumn going towards winter, so temperature lower - air & sea, less daylight etc......
Sounds like you're up for a good adventure.