In your article 'Taking the Heathrow Express to London'
www.bellaonline.com/articles/art69044.asp you mention the fare is from �18 - �26.
The standard single fare is �18. The �26 fare is for the First Class carriage which offers more legroom, a free copy of Financial Times and some magazines to read, but since the journey time is just 15 minutes (21 minutes to/from Terminal 5) doesn't seem worthwhile to pay extra.
If you buy the single ticket online you pay �16.50. Return ticket is �32. Website is at
www.heathrowexpress.comBTW the currency of the UK is the Pound Sterling, not Great British Pounds. What may have confused is that the ISO three letter code is GBP.