Visa-waiver extension Mongolia
 

I am planning to enter Mongolia under the 30 day visa waiver (UK citizen) and then extend to a 90 day visa.

I understand that I need to go to Ulan Bator to do this, but all the information that I have seen says I need to do this within 7 days of arrival - problem is I am arriving from the west and I really don't want to have to get to the capital that quickly.

Does anyone know if it is ok to go to get the extension once the first 7 days have elapsed? Will they fine me or refuse the extension if I do this?

Apologies if this question has been asked before, I did have a look but the only relevant info I could see was quite old and regarding actual visas not the current visa-free system.