I looked at that slip about 6 years ago and decided it was too tricky for me. (I was new at it!) It was also very slippy at low tide and the man in the local boatyard said he had seen a couple of cars in trouble that day. The other main difficulty is you can't turn right at the top of the slip with a long trailer..... and left is a block end, (boat yard actually). So there will have to be a bit of shunting I think! Also it's not very wide and there is a wall on one side and a drop on the other. Other wise it's great! I went and used Queen Anne’s Battery instead.... shallow wide slip, pontoon etc.
Having said that, QAB is costly and I am very mean now. Plus, 6 years ago I had only had my first boat for about a month and I couldn't back-up very well. Since then I've launched at many places including Dover, (which is even narrower), loads of times and not fallen off the edge yet.....
So, to sum up, an ordinary car MAY have difficulty at low tide... (Lots of us have 4 wheel drive so we can help though). It's not the easiest slip but 6 years on I think I can manage it OK. So see what you think when you get there and there's always QAB if you're rich and chicken!