Ooh we LOVE playmobil here! It's pretty much all Ben plays with. He's got loads of dfferent construction/builders stuff (mostly from ebay - crane, tipper truck, scaffolding etc, and loads of builders), and then we've added things like these tiny real bricks
http://www.321toys.co.uk/ctb_m-tef-4090_teifoc_assorted_brick_set.htm and he just sets up whole cities/construction sites.
I like the fact that with the builders stuff it means he can incorporate his other toys into the play at the same time - so he'll 'build' a new road, and have traffic lights/barriers/traffic cones stopping his cars in traffic jams, or he'll use duplo or wooden blocks to build buildings for the playmobil chaps to work on. Or get the train track out for them to work on. Oh, we've got lots of rocks that he tips out of tippers etc too. So there is lots of ways play can be expanded, which is why he is happy to play with it for several hours a day and has done for the past 18 months
!