One other consideration is that the airport may only allow de-icing to be performed in certain areas due to the drainage system. In nearly all main UK airports the drainage system on the stands takes away all the waste fluid to be filtered and processed so harmful waste is not realised into the surrounding environment.
Additionally it was always argued that as severe weather was only a rare occurance it was not worth the additional cost of building/maintaining de-icig areas around the holding point, and that the very days of disruption caused was acceptable.
Rgds Bondy