On the whole, India has become incredibly accessible due to fantastic international flight routes that are often direct, reasonably priced and at a convenient time. Outbound flights are normally overnight landing in to India around breakfast time, and inbound fights normally depart in the morning, landing the same day in to the UK, around early evening.
From the UK, several major airlines (British Airways, Virgin Atlantic, Jet Airways and Air India) fly direct into Delhi, Mumbai, Chennai, Bengaluru and Hyderabad. Direct flights mainly depart from London, but the occasional airline/route will fly direct from Birmingham.
To fly from regional airports in the UK, or to reach other cities in India that you are unable to fly directly in to such as Kochi and Kolkata, several major airlines (Emirates, Etihad, Oman Air, Jet Airways, Qatar and KLM) offer convenient routes that have one stop en route to your final destination.
Price wise, there are great deals to be found on flights to India. Often, an online flight search engine will show return flights with reputable airlines costing around £400 even during high travel season (Oct – Mar), particularly when booked in advance. At more expensive peak travel times, such as Christmas and New Year, flights can be closer to £700-£900.