External doors now have to be insulated or have an appropriate insulation U-value, e.g. for bi-fold glazed doors. This can cause issues if you want to use, say a feature Oak door, or stable door. Fortunately there are ways of overcoming this including the use of special composite doors.
There is also a huge range of internal doors to choose from, with some needing to have a fire resistance, e.g. between house and garage. Likewise there is a huge number of garage doors available, from simple timber open out pairs, to very high spec insulated sectional upward or roll around doors. The difference in price between these can be several thousands of pounds.
Getting any of these fitted properly can also create difficulties. For internal doors we suggest that having these pre-hung in the factory is a good idea. We will be happy to help you with these as we work up the full specification with you or your architect.