Unpublished material is protected by copyright at the moment it is fixed in a tangible form, and there are often sensitivities relating to its dissemination. In Higher Education researchers may want to control how their unpublished research is communicated for commercial, ethical or other reasons. Unpublished manuscripts, letters and private papers may also contain sensitive material that the creator or their estate may not want to be made publicly available.
The fair dealing exceptions for quotation, parody and criticism and review (S30) do not extend to the use of unpublished material, and the duration of the work (how long it remains in copyright) can be longer than published works in the UK. Therefore you should take care when looking to use them.
You can include third party copyright material in your own thesis or dissertation under the illustration for instruction exception (S32) as long as it is for the purposes of assessment. However this exception is subject to the fairness test and does not to apply to wider publication, or making it available online. Alternatively it may be possible to rely on the exception for quotation or criticism and review (S30).