Scale of the market
In 2004, rabbits alone were estimated to cause economic losses > £100M. [reference: DEFRA Rural Development Service Technical Advice Note 01 – Rabbits. See attached document.]. There is no reason to believe that these losses have reduced in the subsequent 15 years, indeed in 2010 the Guardian reported that there were 40million rabbits in the UK costing more than £260M damage to crops, business and infrastructure (reference: https://www.theguardian.com/environment/2010/dec/15/rabbits-invasive-species-cost)
Additionally, losses due to pigeon damage to OSR crops is also high, with the Farmers Weekly reporting up to £53M losses to rape crops in East Anglia region alone (reference: http://www.fwi.co.uk/arable/scarecrows-back-in-50m-pigeon-battle.htm).
Potential commercial benefit
At a standard application rate of 0.25L/ha, costing £12.50/ha, preventing just a 1-2% loss of yield (depending on crop type) due to grazing herbivores provides a cost effective return to growers (see attached costings sheet).
As it is widely reported from farmers and consultants that losses of up to 20-25% crops can be attributed to herbivorous grazing pests, then the potential commercial benefit cannot be overstated.