The time to do this sort of job is nowish, really - though I would probably recommend doing the conservatory first and then the garden can take shape around it, and also stops any damage being done to the new garden by the conservatory builders materials. Turfing can be done in spring or autumn; which part of the country are you based? Try not to just pick a turfing company at random from Yellow pages, you are better off getting a recommendation from someone else - look out for someone having turfing work done and ask their opinion! Failing that, try online some of the gardening networks - I use www.landscapejuicenetwork.co.uk for advice of this nature, and have found the members really helpful.