I would consider very carefully before you put DGS as a first choice - they were apparently the most over subscribed Kent Grammar School in the county last year. My son achieved exactly the same mark as your son (spooky!) and we are only 1.7 miles away as the crow flies in Dartford. The cut off for Dartford marks last year was 351 so highly likely that the OC scores would be much higher. We have the dilemma and we live in Dartford as whether we put DGS as a first choice if we dont get in then we risk having to take whats left as all the Grammars around are over subscribed. My DS also passed the Bexley test and we have to gamble on putting BETHS as a 2nd choice so will probably have to put WilmingtonGS. I wish you every success but this is a minefield I didnt envisage when we got those delightful results!!
Why wouldn't you put Wilmington as your second choice? Do you like Beths better for your son?