For what it's worth, my opinion would be definitely to base the aircraft at an H24 airfield - something Lydd/Ashford is not nor ever likely to be. There is nothing worse than being hamstrung by restricted operating hours when the freight arrives late for example, or a last minute charter cannot be bid for as your aircraft is effectively grounded.
The advantages of SEN are that it is H24, is well known as a light freight airport so has the infrastructure, is located sufficiently near London and the M25/M1 etc. and is (I assume) looking for new business so may offer a good deal to a new operator.
Lydd/Ashford is just too remote in my view for this type of operation, which demands maximum flexibility.