Hi Andrew welcome to the Club
Because the tides around Poole are a little "special" with a double high tide between lows, it is not just a mathamatical equation to work out the Slack periods.
Most of us look at the LW times and work from there
LW Thursday for Poole 15.15, and the tide is fairly small so the flow should not be too strong.
It would be really usefull for you to get a tidal atlas for the area, these are based on HW times at Dover.
a rough guide is Slack in the channel is the HW Dover and HW+6 hrs Dover
Thursday HW Dover is 10.09 and 22.23
slack in the channel will be about 10.00 and 1600
I can not advise on what weather you should go in. [Obviously the calmer the better] as I do not know your experiance.
The decision is yours alone, my advice would be not to push your limits
If you think it is not good enough, do not go.
ref the wrecks
On the drift you need clear water and that is probably a little further off
at anchor the vis does not matter and the closer ones can do well.
The good news is that the numbers on the wrecksite are fairly accurate so with patience you should find them. If new to this pick a good big one that stands well above the seabed.
If its just the wrecking experiance you are after look at the huge Aeolian Sky
Its more than 10 miles away but not far offshore, let the ebb tide push you there and the flood tide push you home.
Look it up on the site, but just in case its invaded by divers look at a couple more in teh area as well.
I expect that others will add more info
PM me if you need more help.
AS I said earlier, Do not push your limits
If in doubt do not go.
Charlie