I get royal mail to do mine, £36.00 per thousand for new customers for around 6 months. Minimum spend per campaign is £500.00. I have been doing some myself but I get royal mail to do the city, sorry too many stairs and apartment doors.
One beauty of doing it yourself is you waste less by not putting them through letter boxes you know wont do any good for you. Like empty houses, the ones that makes you happy you don't live on that road, the ones that could force dulux into bankruptcy and the ones that have no letter box just an open door. Doing it myself opened my eyes, I would not let royal mail do certain areas as you are bound to loose out on half your flyers.