I am hoping to see if I can draw on people's experience.
A friend and I are attempting to enter the Mongol Rally, in which you drive a pretty low quality car from London to Ulaanbaatar (July- August). All things are coming together but getting a place is tough, the first round places were snapped up in 2 minutes.

The logistics and planning are pretty essential. I have spent a few months looking over maps and reading travel guides but I was wondering if anyone would be able to give personal experiences of problems we may encounter en-route.

At the moment the route we plan to take is not the most direct but includes a lot of places we would like to see.
Roughly it is; London- Istanbul- Tehran- Samarkand- eastern Kazakstan- southern Siberia- Ulaanbaantar

London – Istanbul – looking at it this should be the most straightforward part of the trip, we both know the continent pretty well and we are looking to get this over as swiftly as possible. It looks like we may have to take a route via Prague as there is an event planned for the second night of the rally. I was hoping to then see Rila Monastery as the only real diversion on this leg of the trip. Is it true you can stay there overnight?

Turkey – Head across the Central North of the country toward the Iranian Border. It misses the WHS I would like to see but I think a trip back to Turkey would be on the cards at some stage anyway. I don't think that Goereme would be a place that would be best appreciated on an afternoon 'pit-stop'. Are there any places or hazards we should be aware of in this area?

Iran – This is where things can get tricky mostly on visa-based issues. Ideally we would like to take a more circuitous route here heading further south to Esfahan before heading back up to the Mashad. In July/ August would this route be advisable for Two Englishmen and an Irish lass whose idea of a hot day is 25*C?.
If we can only get a transit visa then we can just buzz straight through with Tehran as a mid point for perhaps an overnight stop.
Does anyone have any experience of getting to the three North western Iranian WHS; Soltaniyeh, Takht-e Soleyman or the Armenian Monestries?

I hear that Iranian standards of driving are not the best and I think Central Tehran is a place we will hope to avoid at all costs, at least in our own car. Does anyone have experience of driving in Iran at all?

The Stans- From Mashad we hope to head north through Turkmenistan, very conveniently Merv is on this road. Then we hope to cross into Uzbekistan taking in at least Bukhara, Shakhrisyabz and Samarkand. For me this is the main aim of the trip. Samarkand has been a goal ever since I saw a picture of the tiles on the Registan square so maybe a bit of a break here would be nice. From here we would carry on north through to Kazakhstan perhaps with a detour to Turkestan to see the Mausoleum. The Kazak leg is currently the one I have least researched so if anyone has some knowledge to share it would be much appreciated.

We have taken into consideration that the Visa costs and 'fees' to get through Police blocks will be pretty substantial on this leg of the journey. Again any advice on how to avoid/ deal with these additional fees is welcome.

Russia – Mongolia - Here is where the route becomes hazy. We are trying to work out the best way to get from the Kazak border to Ulaanbaatar. Would it be best to head up towards Lake Baikal and come back down to Ulaanbaatar? This route is much longer but 'road' conditions in Mongolia seem very treacherous and we will not be in a 4x4 so it is looking pretty tough.Are the Roads in this part of Russia any better?
I have just finished watching Ewan McGregor & Charlie Bormans's Long Way Round and it was a bit of a reality check on this part of the journey.

There are an awful lot of questions there but if anyone has experience of travelling in any of these areas then any knowledge you could share would be greatly appreciated.