If you don't have an IMC you need a high level of confidence that you'll have a good horizon and that the cloud base will give you adequate terrain clearance.
In the UK that can stop you any time.
Even with an IMC unless your destination has instrument approach facilities you can still get stuck.
I recently ended with an extra night in Alderney, because I believed getting into Kemble was too risky notwithstanding a Saratoga with all the Nav kit you could wish for and a current IMC!