Thanks for everyone's replies, ditchcrawler thanks for the link i'll have a look and see what's on offer. Alan de Enfield, we need some natural light for during the day as its a bedroom for the teenagers at night and a snug for them during the day! Athy, yes the purpose of putting the hatch in, is for a means of escape if required plus the benefit of natural light during the day. Stilllearning, under the tug is for the kids to sleep and a good little space out of the way to lounge during the day, each to their own I guess, it would be a boring world if we were all the same. Halsey, that's the type of thing we had in mind but to ideally incorporate some day light. I'm guessing you've seen Georgian star in her previous adventures? Not planning on changing the kitchen layout so have a couple of way to access the tug deck.
Many thanks.