There's a 6am coach from Birmingham that gets to Heathrow at 08:50.

One quick thing - whilst I absolutely don't wish to jump to any conclusions about anyone's age, it's worth noting that those 60+ benefit from half-price coach travel with National Express (or an "Up to 30% discount at peak times" - I'm not sure how they define 'peak times') - more info here - to take advantage of this one needs to specify "60+" rather than "adult" during the booking process.

Oh, and Birmingham Coach Station is all new and snazzy - e.g., see this photo.