My little bit of advice would be rather than going from A to B on a short journey in the rain, go out and stay out in it for a while.
I used to get called into London quite often to go to film sets and had to get there as quick as possible.
Riding in the centre of London is traumatic enough anyway, but add rain in the mix and it all becomes a bit manic.
But i find that once you're out in the rain for quite a while you actually tend to forget about it, and i find myself riding the bike much more aggressively by the time i get back than when i first started out.
Saying that, it still falls back again on having tyres that you trust in the wet.
If you have little faith in your tyres then you will become rigid when riding, rather than relaxed, and it will make for a very uncomfortable journey every time you go out in the rain and lean the bike, and you really don't want that at all.
It's all about having a good feeling and rapport with the bike and the road, and the only way to learn that is by getting out there and practising!