IFR in a squirrel
Disregarding the requirement to have two engines, the differences between an IFR machine and a VFR machine -which could also be a twin squirrel - are vast. Actually, the days when you can go IFR overland in the UK are limited due to icing and performance, not to mention diversion fuel requirements etc. I would have no problem going IFR/IMC in an IFR squirrel, but flights would still be subject to strict weather criteria. When the weather is marginal, you often find that the only helicopters flying are the VFR ones!
Are there any helicopters in the UK with a full icing clearance? I don't know of any.
I think that the problem stems from the way helicopter flying is sold. There are countless magazine and newspaper articles informing people that using a helicopter is three times faster than driving, will cost less than a car per mile, and can land and take off anywhere. The reality is somewhat different, but the flying school won't tell you that. By the time the newly qualified pilot finds this out, they've commited themselves to a great deal of expense.