Duncan you can get insurance at the Border it is third party only, It will cost about £15 to £20 for 30 days cover if I remember correctly it is obligatory. If you are stopped without it -you will find it a very big problem and will at least get a roadside fine but maybe worse depending on the police.
The Border you will need your original V5, driving licence, international driving licence(This is the only one I ever show) Carry as many other bits of official documents in a folder (MOT, UK /EU insurance ETC etc) this keeps the border guards busy and happy they love paperwork. You will need to get a temporary import certificate for your bike, a customs decleration and a migration card. You need a visa and invite to get in to the country (try getrussian.com) I found them very good. I also found it helpful and eased the border guards by having a rough translation in to Russian of my paerwork. No one tells you or helps with what you need but I was lucky and the border guards were in good humour. Give big smiles a little Russian Language and everyone is fine. I would stay in Hotels or registered campsites of which there are some - and dont be put off Russia as you go through nikel on route to Murmansk - Its like hell on earth but the russians are really great love bikes and like it that you visit them have a great trip. The roads are rough in places but take your time you will be fine. In st petersburg i can reccomend appartments in the center which are far cheaper than hotels and very secure send me a PM if you want to know more - or come along to dent 3rd Northern Mini meet and have a chat .