I only really use Heathrow about once a year , but we always stay overnight the day before our flight and have a parking package included too , the first few times we always stayed at the Sofitel in T5 ( our flights have always been T5 ) which was very convienient as its attached to T5 and you only have to walk to the checkin area , the parking there is also very good and under cover too .however it started to become quite expensive staying there and I looked at the Hilton at T5 , it's only about a 10 to 15 min hoppa ride away and the parking there is also really good and safe , the rooms are excellent The restaurant is also very good and the breakfast which is best to pre book with the " breakfast included rate " is really worth it . I've always found the staff there to be really good , polite and helpful and the layout of the hotel is superb in that you're not having to walk around for ages to get somewhere and it's very easy to navigate and find your room ( unlike the Sofitel ) . There is also a holiday inn along the road that is located along the same hoppa route H57 , that might also be worth a look at depending on price / parking etc .