Hi old man!
My partner and I did it two years agon in Devon around March, 'kin freezin weekend that was too, so my advice would be wrap up warm in multiple layers. If you have any cycling or ski wear, get it on. Then you won't have too much bulk but can peel layers off if it warms up.
Other than that, sleep well so you have a sharp receptive brain when you go in to the classroom. it really isn't difficult at all and can be great fun if you have a good trainer. We were lucky, our guy Paul at East Devon training was easy going and very laid back in his teaching. Both the misses, with no previous boating experience, and i were ripping it up across Torbay in a 2 metre swell at 30 knots with confidence on day two. In a 6.5m Rib we had never piloted before. Go get em'!