Damp patches on ceiling which trade to call?

Woke up to wet patches on bedroom ceiling, the patches are now dried out stains on ceiling and bedroom has now got an awful smell. Directly above is the loft and roof space. Has been insulated in 2013 by British gas. Was pretty bad weather when patches appeared (snow and storm) so may be due to that. Who do I call? Builder / Plumber / roof guys? Buildings insurance won't help as they don't investigate a problem they only try and fix what we tell them is wrong!! Note to self change insurance company!! Help. Thanks in advance