Can anyone recommend a good book on what to grow in a cold greenhouse?
Do you mean ornamental plants or edibles Alex ? In containers or in borders ?
edibles in summer but maybe ornamentals for winter. I tend to stick to tomatoes, cucumber & chillis in summer and although these are very successful, I'm getting a bit bored! My greenhouse is an interesting hobby rather than something just to produce food. I want to try something fairly foolproof but a bit different. Everything in pots.
I've got 'The Collingridge Handbook of Greenhouse Gardening' by Macself and Turner, Hamlyn 1982, ISBN 0 600 36809x. I think I bought it in a sell-off at the library and it is excellent, with detailed cultivation information on a wide variety of ornamental plants, which doesn't really change much with time, though of course the stuff about the greenhouses, heating etc is out of date. You might find one on the the secondhand market, or a more recent edition if there is one, that's if no-one can recommend a better choice.
I find that the houseplants around today are much less varied than those my mum had when I was a child, and many garden centres hardly bother with them at all, but quite a lot of things are available as seed, if you are prepared to make the effort. And of course there are new things to try now that were more specialist then - I've grown plumbago, coronilla glauca and ivy leaved pelargoniums from seed for greenhouse use.
What about making yourself an Alpine bench ? Lots of interest with these plants and plenty of books on the subject. Depends tho because that would mean permanent staging so cuts down on floor space. You could do the same for Cacti if you like them. I keep mine in a cold (insulated in winter....no heater ) G/H over winter. Orchids maybe ? I have Cymbidium and Dendrobium..........G/H in winter and indoors when they start to flower. A Passionflower......not the basic one but maybe Constance Elliot ? In a large pot and trained up into the roof space. I'm trying the P edulis this year. Bonsai ? A good subject for a cold G/H and plenty of interest there too.
A hot bench to raise seeds of stuff that takes your fancy or to grow cuttings ? More economical than a propagator. Again, there are good books on the market to cover just about every sort of plant.
Once you've decided, ask again about the books.......specific subjects will help people to make relevant suggestions.
Hope this has helped a bit. I'm sure others will be along to offer their ideas.