Pinetops grows lilies, poinsettias and hellebores professionally and has been planning a move to the former HRI site in Efford for several years.
Pinetops will be moving to its new site at the beginning of 2015, with the old site going for housing.
The pumpkin measured more than 5m in circumference and weighed 854kg, a British record but well behind the 951kg world record, set by Ben Meier of Switzerland this year.
The Patons reclaimed their UK title from Dorset dairy farmer Mark Baggs.
Thompson & Morgan is harvesting the seeds, testing them for viability and preparing them for sale.
T&M sell it under the variety name Pumpkin ‘Paton Twins Giant’ at £9.99 for two seeds "with the genetics to become a record breaker with the right care".
Stuart Paton said: "We’ve always been confident of getting the world title eventually and it’s brilliant to be installing a new greenhouse for 2015 on better soil with better drainage and twice the amount of growing space. We should be all set to take on the Americans and the Swiss."
T&M promises to pay £10,000 for a UK world beater.