When buying them, what should I look out for in terms of quality and price etc my size is 225/40/18

hard to answer that as we don't know what your priorities are : dry performance, wet performance, snow/ice performance, noise, price, brand recognition, how long they will last

As above....

My priorities are dry/wet grip and least is cost (although I try to get the best deal I can of course), so I normally end up spending £180 per tyre which last about 15K miles...need 4 next year 😂 when I swap back to them from Winter wheels/Tyres. 

However many members on this forum, that will be the number of different recommendations you'll get. If you don't have a budget, just buy the most expensive you can afford, if on a budget, you can still pick up brand new roadworthy tyres for about £40! (Like I did...) 😃

Hi thanks all for your input.

Just everyday use I guess.

Do all new tyres have the same amount of tread in millimetres, how can I tell which tread is better

I have found one for £46 Inc fitting but I can't tell if it's any good, why is the £63 one better?

 

Those two are quite similar. The cheaper one has a slightly better fuel economy rating (C is better than E by about 3%, although tyres only account for about 20% of total fuel used). Both have similar wet weather performance (B). You won't notice the noise difference between 72dB and 71dB. All new tyres have the same tread depth (about 7mm) but some compounds are harder than others and will last longer (the tyre label doesn't show this important bit of information). 

some tyres have rotation direction arrows on. I don't like those because it restricts how you change change the wheels round on the car eg if you have one which wears down edge more and you want to move them round to equal up the wear. Neither of those two look like the tread is directional, unfortunately they don't tell you.