One correction in the article -

"Despite a short-sighted transit immigrant visa requirement and ridiculous air passenger fees, Heathrow is a major transit point for passengers between India and North America."

That is precisely because while India is on the list of countries that require a DATV (direct airside transit visa), there is an exception in place - that you don't need a DATV if you have a valid visitor visa to the USA / Canada / Australia / NZ, and you are transiting LHR en route to those four countries. The same exception applies if you have a Schengen long term residence D visa.

What is noticeably missing is an exception that says "Schengen C visa" - a short stay tourist or business visa. Which means any trip to the Schengen region via the UK requires a British DATV. Which costs UKP 50 (soon to become UKP 40 I think) and an incredibly detailed visa application form, with all the usual extra documentation demanded .. tax returns, salary statements etc etc.

Which means - don't ever fly BA from India if you want to go to say Brussels or Paris or whatever. Fly QR and earn a fraction of the tier points / miles on your BA executive club unless you buy near full fare economy tickets. Or just fly LH / AF and use your schengen visa to enter Europe in Germany or Paris before you transit onwards.

One additional exception is Ireland, which has a complicated process where if you get a UK short stay visa, stay a day or so in the UK and then go on to Ireland, you don't need an Irish visa .. just the UK short stay visa. Note - if you simply transit through LHR airside and fly into Dublin with just that UK visa .. that won't work. The irish immigration looks to see entry / exit stamps on that british visa before they let you in on this exception. http://www.irelandinindia.com/home/index.aspx?id=86830