[rhyds]

Garden hose might do it, but personally I'd dig in some rigid plastic drainpipe, as you've then got extra space to run stuff like phone extensions in if you need them. I take it the summer house is powered, how does that cable get there?

The problem with taking the DIY option is that VM installations are very sensitive to interference and power levels. A length of dodgy coax can cause interference not only to your equipment, but to other VM customers nearby. If you're careful however you should be OK.