Flights to Europe

You are going for two weeks with three public holidays in that period, it sounds like your are trying to fit too much into too short a period. You are also flying at the MOST EXPENSIVE time of the year so asking which would be the cheapest way to do it is a bit pointless, doing the trip a few weeks earlier or later is the answer to that. Doing an open-jaw trip from Toronto is one possibility to save money; Ryanair and easyJet are the largest two budget airlines from the UK, just make sure you understand all their terms and conditions, they say what they mean but they also mean what they say and those who cannot figure out that this applies to them usually end up paying a high price for it, like Ryanair requires you to print your own boarding pass, warns you with e-mails to do it, and if you ignore them charges you a fortune.

Thanks for the advice. My friend and I both get our Holidays on that 2 week period so we need to go during that time. I realize it is expensive I just thought maybe someone had done it before and was able to find a better way.

There's expensive and then there's Christmas, but hey ho...

Given you have only 15 days and there are 3 bank holidays in the way including one where everything shuts down (Xmas day - I do mean everything), I'd stick to max 4 destinations (as in locations, not countries). Getting around will be problematic (pricy, and/or lots of roadworks and rail engineering stuff going on). :-)

Bear in mind that London alone could keep you occupied for a week, ditto Paris.

PS - Flying around on Xmas Day itself is surprisingly cheap, but getting to/from the airport is surprisingly difficult.

Do you think seeing those 4 countries would be to much?

16 days for 4 countries=4 days per country... even less once you exclude travel time among countries as well as your arrival and departure days...
With your timeframe, I would suggest to focus only in one country or in a region within it.

oh dear - please check a map. You could 'do' quite a lot of London in that time. But as others note, all that rushing around just won't work, especially in those two weeks.

don't fly on Christmas Day and remember that EVERYTHING will be shut then. No transport in London at all and probably none in other places either.

London is not a country !

Basically you want to see 4 cities, you are not going to see Germany, France and Ireland in that time schedule. If you are going to visit different cities, the airlines you want to look at are easyjet, ryanair especially if you starting and finishing in London. www.skyscanner.net is good.

But as others have said the time of the year and the time you have, it's a bit crazy to think of doing this. What's wrong with actually visiting other parts of the UK, London is not the UK

Book flights early even now on most routes and definitely UK / Ireland destinations. Expect little public transport on 26th December - Boxing Day (St Stephen's Day) in Ireland.

The assumption is that you only have walk on luggage otherwise you will find you pay dearly particularly on the budget airlines. Important to read those T&Cs as others have pointed out.

UK train services do not usually announce engineering works until 12 weeks before Christmas.

Expect it to be dark after 4.15pm in UK at that time of year which may be pertinent for some sight seeing.

R