Maybe my mind is just conjuring them up, or perhaps the bill stickers just put up what they're told, regardless of relevance...
They usually are, billboards are categorised accross the UK, so they just go up.
What has been interesting is the HDM delivering Talk Talk leaflets in with the Advertiser free newspaper using this service
http://www.thisislocalleaflets.co.uk If I was from Talk Talk, I'd want my money back.
BT are also advertising on East Riding busses on routes that just go round Hull.