CK - I regret that these issues were not covered during your IMC training - becasue they should have been. Unfortunately this would seem too often the case.
There is a suggestion from your post you may not be clear on the difference between IMC and IFR. Any pilot can conduct an IFR flight however for that flight to continue into IMC then the pilot must have an IR or IMC rating.
You can file an IFR flight plan within the UK which may include flight in IMC and you can change from visual to instrument flight rules in flight because you have entered IMC.
Your landing minima are the same as the minima for IR holders (although this has been widely debated and there are those that would disagree.) Whether you should operate to these minima is another matter.
The rating is restricted to the UK but it does "lift" the requirment to remain in sight of the surface outside the UK - commonly know as VFR on top.
You are entitled to operate in IMC in all UK classes of airspace except for all types of class A.
Flying a solid IMC sector with an approach to or near minima followed by a possible diversion is not something the IMC rating has probably trained you to do safely (although it is within your priviliges) but there are many IMC rated pilots who with further training and experience do exactly this.