The fare spreadsheets, with fairly up to date fares (but not exact as it is a volunteer effort), is linked to by the sticky at the top of this forum. You might notice that originating in Stockholm would save you several thousand pounds (similarly for GIB). The prices vary widely by product and country (the cheapest for DONE4 is often not the cheapest for DONE5, for example, or for AONE4). The key restriction to keep in mind is 2 stopovers in the continent of origin. Often people use an award ticket to position to the start of the RTW. Sri Lanka was one of the cheapest places to start, and that limits your 2 stopovers to Asia (instead of Europe); so it all depends on your plans. Unfortunately there was a fare increase Sept. 1, and not sure where the fares are right now for each country, you will have to check for the countries of interest to you. Chances are CMB is no longer so attractive on the fare, but still cheaper than the UK.

Surface segments never count as a segment, but do make each endpoint a stopover (of significance only in the country of origin, as the fare allows unlimited stopovers in all other continents). As for breaking up a RTW, generally you can easily create 3 separate trips out of the one ticket, with the 3rd being a LHR-DXB-LHR loop at the end (something you cannot do if your ticket originates in the UK, instead of STO, GIB, etc).