Despite all those train promotions, a flight is still the quickest way to get from Scotland to London. With cheap Easyjet flights to 3 London airports, you can usually find a bargain deal.
Easyjet (www.easyjet.com) flies from Edinburgh and Glasgow to London Luton, London Gatwick, and London Stansted, and from Aberdeen and Inverness to Gatwick and Luton.
It's not too difficult to pick up Easyjet's lowest fares. These are £21.99 one way from Aberdeen, £18.99 from Edinburgh and Glasgow, and an amazing £11.99 from Inverness (you can even snap up a remarkable fare of just £8.99 from Inverness available in October).
The return legs from London tend to be much the same price, although you'll pay a minimum of £21.99 for an Inverness flight. These fares include taxes but don't include additional charges for baggage and credit card fees.
On arrival, it's easy enough to find public transport into central London which is fast and runs regularly. The London airports are all well-connected by direct trains to London.
The Stansted Express (www.stanstedexpress.com) runs from the airport terminal into London Liverpool Street. Single tickets are £30, and returns cost £32.50. Railcard discounts are permissible.
The Gatwick Express (www.gatwickexpress.com) offers direct services into London Victoria. An anytime single ticket is £17.90 and an anytime return is £30.80. Tickets booked online are around £2 cheaper.
From Luton airport, you need to take a shuttle bus to Luton Airport Parkway station. Trains to London St Pancras take 27 minutes and tickets are £12.50 single. The train fares might not be all that cheap, but flights to London from Scotland should fit most budgets.