The kimlik is issued after you have been granted Turkish citizenship, the UK & Turkey recognise dual nationality and it is very helpful for all the above quoted reasons most importantly avoiding the residence permit payments which have recently rocketed or the need to remember a trip every 3 months and the ability to work without the virtually 'impossible to obtain' permit. You can travel easily in and out on your kimlik and British passport, no need to get a Turkish one. If you have a Turkish spouse the marriage has to have lasted 3 years,but you can start to apply before it has by a few months, there is no Turkish exam, but at the Mugla interview they do ask you a few things in Turkish, the ability to mumble something seems to suffice. If you require a med certificate then try the Saglik Ocagi it is cheap, one stop and if you can breath you pass! The one by the tuesday market did mine.
For resident foreigners you have to be here for 5 years and I believe you do have to take some sort of Turkish exam, a few enquiries from friends and neighbours could help with this and maybe the Dept of Education, which is upstairs from the Nufus or population folk. The manager of the 'population' office in the front of the Kaymakam's building can also be helpful about what is needed especially if you have a Turkish speaker with you. He's the guy you see to arrange a wedding date.