London Heathrow to Venice and Rome back to LHR ..which airlines ?

Hi Patrick,
Try checking www.sidestep.com or www.kayak.com to see some of the options. Check the option that also includes nearby airports.

I've flown BA from Rome to LHR.

I recently was pricing flights from London to Venice and found more low cost options out of Gatwick (both BA and EasyJet)

Try whichbudget.com to find airlines, discount and regular, flying between those cities.

We recently flew Virgin from SFO to LHR on frequent flier award, then took British Air from LHR to Rome. We traveled in Italy for 10 days and took BA from Venice to Gatwick, before getting a train to Yorkshire.

It can get complicated, since a number of airlines use different London airports, depending on destination. Be aware that getting from LHR to Gatwick can be very time consuming. Also, fares can vary wildly depending on time of day you are flying.

For us, the schedule was more important than absolute cheapest flights, though we got reasonable fares on BA, and the flights met our scheduling needs. BTW, we found check-in at the Venice airport to be the most difficult of the whole trip. I've no idea how bad it is getting out of Rome.

Ciao.

You should be able to find the information you need here:
http://www.europe-airports.com/italy/