We can all get caught out by the weather - even the forecaster.
I did the mandatory 5 hours instument time when I did my JAR PPL two years ago. Trouble is I havent done any since, other then tertiary use of them during my Night Rating recently. Maybe I really should go up with an Instructor for an hour and do some instruments refresher. Te aim though is not to get caught out by bad weather, but we live in the real world...
Remember this, when the sh^&e hits the fan - aviate, navigate, communicate. Follow that and you have a pretty good chance of surviving to tell the tale I believe.
And remember in the interests of flight saftey the PIC may deviate from the Rules of the Air. So if you have no IMC/IR rating and you are (for whatever reason that may or may not have been under your control) forced into IMC conditions then you are forced into IMC conditions. You depart from the rules for your own safety, declare a PAN or MAYDAY and then sort the problem out.