Hi,
If you have a continuing rental business then these expenses may be allowable as long as they are of a revenue nature and not capital and are wholly and exclusively for the rental business, which is covered in BIM37007 here:
BIM37007 - Wholly and exclusively: overview
PIM2510 may also be of use as it outlines that there are exceptions for temporary pause depending on the level of changes made and also the length of time between lettings. Under the general rule of thumb, a three year period of no occupancy would constitute the ending to the rental business, which does not match your situation.
PIM2510 - Beginning and end of a rental business: cessation
Thank you.