Sure its been said before, but the cheapest solution of all is to ask your local publican nicely for his bulmers/magners/NBA glass bottle empties

For them, they're a waste issue that they dont have to dispose of if they give them to you. I drop the landlord a few homebrews as well every so often to sweeten the deal
I collect from my local about twice a week and get about 30-50 bottles at a time. I then have the choice of storing them, wash/sterilise/use or if I have time, giving them a soap wash and passing them onto other home brewers I know (i've also sold them in x12 lots on Ebay to fund a few kits

)
And should I ever find myself too swamped...a trip to the glass bank would solve the problem
Glass is the way to go - although I keep a few PETs ready in case