Bidders were required to nominate locations in the vicinity of current SAR flights such as Wattisham but alternative locations were acceptable to the DfT if bidders could demonstrate no overall increase in average response times to incidents throughout the UK.
Bidders had to reach all very high and high risk areas and 75% of the medium risk areas (as defined by the UK SAR Region risk profile map) within 60 minutes of take-off. The DfT used a complex 'Vicinity Tool' to verify evidence for alternate locations.
One has to assume that by moving from Manston to Lydd, Bristow are still able to achieve this, otherwise they would be in breach of the tender requirements.