Most of the Hoppas are on a loop, so they go around the hotels listed and return back to the start location (some exceptions). So if you take the LHR depart time, work out approx how long it takes to get to your hotel, then that's also the departure time back to terminal. I'd guess 20 minutes in this case.

However you would be mad to take the Hoppa to the Ibis. Just take any of the myriad free TfL pubic bus services from Heathrow Central (second last bus stop on the main set) to Harlington Corner. No need to look at the timetable, they run every few minutes. If very early or late, the night bus service from T5 goes to Harlington Corner directly.

If you are HBO or with checked luggage to elsewhere and you arrive before 21:30 into T5, take the bus to T2 (no boarding pass needed unless Domestic/Irish), short walk to UK Border, landside and to the bus station.

If you have checked luggage to collect or are Domestic/Irish, then take the tube to T2/T3, bus station is above.