The key to remember with all pollen patties is the bees will only use them when they have no choice. Natural pollen is far more preferred by the bees so if there is an adequate source, they will ignore the patties. This means there is no reason to use them apart from early season, late season, or if you are in an area that gets 'the June Gap' - a period which can last a few weeks where the spring flowers end but the summer flowers haven't started flowering.
The independent beekeeper/scientist, Randy Oliver, who has done some great studies, did one on pollen patties. Although American based, and not all the patties he used are available in the UK, his results showed an improvement in all colonies that were fed patties compared to nothing. His full report can be viewed here: