You can get round the pubs that will not refill a glass by sticking hold of your old glass (or having your own tankard if you want to be a real poser:-) ) and letting the bar staff give you a new glass - Only to pour the contents of it into your old one. Often confuses the hell out of the poor dears. There are good reasons for not refilling btw - Mainly because the older style beer engines have the end of the swan neck inside the liquid being poured. A used glass could contaminate the business end of the pump with any number of bacteria but considering the number of chances for that to happen in hundreds of other places I think they may be being over-cautious. Particularly with the pastuerised 'dead' beers in which no self respecting bacteria would live anyway:-)

Cheers

Dave