I think you'd be wise to discuss this with the bevvy of estate agents that you will presumably invite, when they come touting for your business. I think the answer is 'it depends', and a good agent should be able to offer a rational answer for your particular property and area. Factors influencing could include:
the extent to which you have installed other insulating materials in the roof and walls - DG in terms of insulating value for the price paid is lower than other measures on the list of priorities. So roof and wall insulation are perhaps a better measure, but are invisible to many potential buyers apart from in the HIP Report.
the extent to which DG would help to reduce external noise - if one lives on a busy road, for example
the condition of the existing windowframes - DG is seen by many as a 'fit and forget' future maintenance measure, but it depends what you have now.