If it were me I'd cruise in company first to build up friendships with like minded-folk. By advertising for potential shipmates you're simply going to get a mixed bag, some who are potentially going to be a complete liability when you're out.
I've taken numerous friends out on my boat over the years and it's not for everyone. Some like the experience, enjoy the good days, and others who get bored or are as sick as a dog as soon as the boat comes to a stop in a bit of a swell.
You're Solent based so there's no shortage of potential Ribnet compatriots. Try living in NE Scotland, where seeing another leisure boat on the water is hard enough, never mind cruising with fellow enthusiasts.