People tend to check in during these times:
Walk to Brunel Uni, save money, burn calories
3 - 4 Piccadilly Line trains an hour so if there is not one in the platform take a Metropolitan Line train and change at Rayner's Lane. Travel in the front of the train if it is raining!
For the Brunel students who lives in Isambard Complex: take the bus U5 or 222 and stop at Station Road.
There are two bus routes from here to Heathrow but take the A10. It's MUCH quicker!
There is no toilet here or really nearby. Go across the bus station, to the Travelodge, take the lift up to the reception level and use the toilet there. I've done it a lot and never been stopped.
Go to the pub!