Ah yes we saw a picture of this on another thread yesterday, was it you who posted it up? basically it was a weatherproof socket with 5 mtrs of flex, (not sure what size) and an rcd plug to make it all work, a bit like the washing machine pipes you can buy and connect yourself by screwing into existing pipework, a DIY thingy lol. As to answer your question, yes in theory it is safe, however it would depend on how you ran the cable inside to it, providing the flex supplied is adequate in size, it is certainely something I would recommend you remove immediately after christmas as well, definately a temp thingy, horrible really but there you are.