Train from London to Glasgow starting at Waterloo tube station

Getting from Waterloo to Euston couldn't be easier. No worries there. Take a Northern Line tube train and it's only a few stops station to station. Euston Underground Station is right below the mainline railway station where you'll catch your Glasgow train. Take an escalator from the tube right up to the main station concourse.

You can buy your ticket to Glasgow in advance. When are you travelling? A tube journey is easiest done tapping your credit or debit card at the beginning and end of your journey to pay.

There's basically three public transport options from Heathrow; The Elizabeth Line train, Heathrow Express train or The Piccadilly Line tube train. There's various advantages and disadvantages to choosing one over another, often debated here. Someone better at explaining the ins and outs than I may want to contribute.

You could actually buy a train ticket from London Waterloo to Glasgow- that would include your tube fare. It costs £3 more than a ticket from Euston, so has a slight premium over paying the tube fare separately but has a convenience factor to it.

I am actually doing that in 2 weeks time, even though I have an Oyster Card. In that case I am on the last train of the night to my destination in the North of England (on a journey from Dorset), and that particular Glasgow train runs late over 75% of the time. So paying my tube fare that way is "insurance" because it is a near certainty that I will need Avanti to find me a taxi for the last 40 miles of my journey.

From Heathrow to Waterloo there are two other possible routes-
1- National Express Bus to Victoria (the driver looks after your luggage) then London Bus #11 from right outside, or hail a cab for the short ride;
2- London Bus to Feltham station, then frequent main line train to Waterloo. This is a route beloved by South Londoners (who use it all the time with luggage), and is the route that was used in the days before the tube served Heathrow. Feltham is within London zones so normal payment methods apply.

Thank you both! This was very helpful!