Suggest you mae your way to Vlissigen. Wait for an apropriate weather
window and head
for Ramsgate. Then via the Prince's Channel to the Queenborough in the Medway. Then it's easy to time your run up the Thames with the tide. Have no dealings with the Gore/Four Fathoms Channel. It's very shallow and poorly marked and it only saves you a couple of miles. Not for nothing is it known as 'the overland route'.
Alternatives include Roompotsluis to the Orwell. (I did this in reverse last week). Or head
further down the coast to Oostende before making your crossing.
For more information try asking at East Coast Forum