You can indeed pay for most purchases in Euros, and you will normally get a better rate of exchange for YTL in resort than if you bought YTL in the UK.
However, I always take Sterling, which is also widely accepted in the Antalya region, otherwise you pay two lots of exchange rates.
However, if you do take Sterling ensure that it must be English Notes - not Scottish.
You can then pay for major shop purchases, trips, hotels etc in Sterling at a good local rate of exchange, or take your Sterling to an Exchange Office - they post their rates of exchange in the window - but check in advance whether they charge commission. You will definitely need YTL for your smaller day to day purchases, such as supermarket, bars, buses and taxis etc.
You will also get a very good rate of exchange at the ATM's - which will dispense lira against your debit/credit card, but be aware of the cash advance fees/daily limits imposed by your card issuer.