I'm not sure whether you're looking at boys or girls schools, but there's no question that the Kent schools are much harder to get into now if you're OOC. I'm pretty certain that from Bexley you'll have probably (I could be wrong!) a zero chance with Gravesend and Mayfield. In the past Wilmington boys may not have been a problem, however their catchment halved last year, only going out 2.5 miles OOC as the crow flies (from over 5 miles the year before). This means that Crayford, Barnhurst, top end of Bexleyheath and Bexley village will have got places but that is all. I'm aware of someone in Bexley Village who just missed out last year.
I'm not sure how far Wilmington girls went last year (I know it went out to Danson) but I think they took an extra class. I don't know what their PAN is for this year, but I'd guess that given the Ofsted Outstanding it was awarded a year or so ago, demand will be even higher than last year, I have many friends whose children have passed Bexley and Kent and yet, despite having Chis & Sid, Townley etc. on their doorsteps, still want one of the Wilmington Grammars. I think that there's a chance that Wilmington Boys catchment will shrink even further than the meagre 2.5 miles it was last year.
It was the same for my DS, he chose Wilmington over Beths, despite living less than a mile from Beths, but it was his choice (we're only 2 miles from WGSB, so there wasn't really much in the commute). Likewise we know plenty of parents who children attend Beths or Townley yet they live the other side of the Bexley border and come under Kent ...
Lefol, I know it's not necessarily what you want to hear, all I would suggest is that you visit the schools, put them on the CAF in your order or preference and hope for the best.