If you have both a uk and canadian passport, when you fly to the uk for a visit which passport do you tend to use?
Can you fly there on the uk and on the way back on the canadian? Do you run into any issues just flying on the canadian one when you land in the uk, I.e having to go through passport control?

If you have both a Canadian and a UK passport then its simples

UK one to enter the UK
Canadian one to enter Canada.

Ok great, wanted to make sure there were no issues with that. I'm applying for a canadian one shortly as just got my citizenship

When I buy my ticket which passport number should I enter though? Does it matter?

Exactly what I did when I just travelled to the UK and back last month, no problems

It doesn't matter, but if you need to scan a passport at the airport check in machine it has to be the same one you registered when buying the ticket.

Carry both.

Which passport information did you put into the advance passenger information?
I assume from the posts above it did not matter that on one of the flights the advance passenger information didn't match the passport used to get into one of the countries.
I am flying back to the uk on 27th August and it will be my first time flying as a dual national

If you're just visiting the UK, you can use the Canadian passport only for the entire trip. That's the simplest solution.

If you take the UK passport with you, you can use it to go through the EU line when entering the UK. Once, after I did this, I was challenged in the UK airport (on the way back to Canada) as to why there wasn't a UK entry stamp in my Canadian passport. I replied that I had entered on my UK passport which I was then asked to produce. So if you're going to act like a dual citizen, make sure you can produce either passport at short notice.

No problem for me to carry both when I travel. The non-UK lineups at Gatwick and Heathrow are outrageously long.

On a recent European trip arriving late one night in LGW from Spain & returning to Canada the next day, I opted for the Non-Eu line & my Canadian pp. The line was shorter but a lot slower & I didn't really get through any faster. Plus I had to explain to the Border Officer why I didn't have an entry stamp into Spain (or anywhere else in Europe) in my Canadian passport. I thought she was going to make a thing of it but it was late and she stamped me in.

I book everything using my Canadian passport. I use my EU passport to enter the UK, but do all my check-ins etc using my Canadian one, then I present the Canadian one back in Canada. But carry both all the time in case you are asked why you don't have stamps etc.

I book on whichever passport is closest at hand. If I travel to Europe I enter using the British passport and show Canadian one on return to Canada. I always carry both passports, unless I am going to the States in which case I leave the British one at home. Never had a problem.

Id always choose to enter the UK on a UK passport for this reason.

In the past Ive had an expired UK passport with me and gone through the shorter UK lineup on my Cdn passport with no problem.

Another time I was seen in the non UK line with my UK passport waiting with my family (all Cdn passports) and we were all invited to joint the shorter UK queue

Same thing happened last time I went to the UK with my girlfriend, except I wasn't as chivalrous as you. I took the UK line, she took the non-UK, with a "I'll meet you in the bar!". When she eventually got to the border guard he told her she could come through with me next time!

I, like you OP have not flown as a dual national yet, only recently got my EU citizenship. But i'll probably (as long as resident in Canada) book all flights/do checkins with Canadian passport, and present the EU one upon entry/exit to EU countries. On coming back into Canada i'll present the Canadian one obviously. As others have posted always best to enter/exit the UK on your UK/EU passport rather than the Canadian one. Its faster and there is less hassle.

Canadian passport info for advanced passenger whatever/airline/check in, only use the UK/EU passport for entering and exiting the UK/EU.