I am a member down there as I have a house locally. The club allows rentals. You have to join and have a one hour checkout flight with the very intimidating CFI Sheila!!
They have a number of the usual fleet spam cans, 152 and a warrior as I recall.
The club is very friendly and theer prices are competative.
Be warned though, the Cornish weather is VERY unpredictable and the aerodrome is difficult to find and has a LOT of runways very close together and it is easy to align yourself with the wrong runway. I have flown out of there many times in perfect sunshine without a cloud in the sky and returned an hour later in pouring rain and 600ft cloud base.
The hopper flights run in and out of there to the scillies and they land and take off on the most conveniant runway to them which can quite often be straight accross your nose!
I will post the phone numbers and emails this evening.