Canterbury to Heathrow by train

You will need to transfer stations in central London. All trains to Heathrow leave from London Paddington. What I could see from National Rail's site was trains usually come from Canterbury into Victoria or Kings Cross. Assuming the circle line (the Underground) is running it is a straight shot to Paddington from both of those.

Quickest is a train from Canterbury West to St Pancras (about 1 hr) – look for Advance tickets £12.80

Buy from the train operator. This page tells you when they become available for your travel date.

https://www.southeasternrailway.co.uk/help-and-contact/faqs/tickets/advance-tickets

Then Tube (Piccadilly Line) from St Pancras to Heathrow (about 1 hr).

Ramblin On has given the best advice. Canterbury West to St Pancras, then follow signs to the Underground and the Piccadilly line to Heathrow. Very easy.

If you choose the Paddington option it's two changes.

That’s my local train line. It’s definitely quicker and more reliable to take the high speed line into St Pancras then head to Paddington on the Circle underground line then take the Heathrow Express train. Taking the Piccadilly line all the way out to Heathrow would take longer, but involve fewer changes. See tfl.gov.uk for route options and live running information.

You need to check on the southeasternrailway.co.uk website nearer the time to see if there is any planned engineering work taking place over that weekend - the last thing you need is a bus replacing the train for part of the journey which could add an hour to the travel time.

I would allow a good margin for potential delays.

Is London on your itinerary this trip?
Perhaps you could make things easier by putting London at the end.

the third rail train from Canterbury to Victoria or Charing Cross is slow and usually has lots of stops. The high speed Javelin train from Canterbury to St Pancras is fast and comfortable with lots of room for luggage. Then either Piccadilly tube direct to Heathrow, or Circle Line to Paddington and Heathrow Express from there... you could take a taxi from St Pancras to Paddington... my personal choice would be the Piccadilly as long as it isn't rush hour... Saturday morning it wouldn't be - but as said above check your route for weekend engineering works...

Thanks to all. This is really helpful.