I would like to know what is the best way for me to travel from Edinburgh to London (one way) and I would like to include a airport voucher from London to Heathrow if possible. Oh I could include a side trip to Cambridge from London.
Walk up fares for long distance trains in the UK are very expensive (often over £100). The key to getting cheap fares is to book 60-90 days in advance.
For day routes, book at www.nationalexpresseastcoast.com. Fares can be as low as £14.
For the overnight Caledonian Sleeper, book here: http://tinyurl.com/g9ehd. Look for Bargain Berths which can be as low as £19.
We actually are taking that same route in about 2 weeks. Taking the national express east coast on a sunday evening Edinburgh to London City center and we are paying 32 pounds a piece. We only booked a month in advance. Good luck. Hope you are as excited as we are in visiting Scotland.
Do book it in advance to get the best rate. The east coast route has been easier in my experience as there is frequently work on the other line...particularly on weekends. Maybe it's over now, but it's best to be aware.