Just by looking at the area near LHR there is a Raddison Blu right next to the Renaissance, Park Inn by Raddison London Heathrow, Sheraton, Thistle London Heathrow Terminal 5, and a Hyatt.
The Thistle Hotel at T5 apparently has good views from its aviator restaurant. They seem to have an outdoor seating area and it’s located opposite 27R/09L closer to the 09L end.
Haven’t stayed there but worth a look.
Wherever you stay check which runways are in operation as they alternate the arrivals and departures between the north and south runways each week which might affect your view
Worst case book an affordable convenient hotel and venture outside, loads of spotting points around LHR