There is another fan to draw air into fridge compartment- access via fridge: remove back panel (long plastic cover- just clips off). Remove control housing (again, just clips off- careful of wiring though). Fan is located up in this channel between fridge and freezer compartments. However, from what you are describing, I think you have a blockage in the freezer drain, causing a build up of ice in the freezer which blocks the air flow to fridge.  To check, remove rear panel of freezer (clips off- you need to press down two clips at top of panel, they can be tricky to get off!!). Disconnect fan motor wiring by unclipping plug connection, and remove sensor wire(white wire) so panel can be removed completely. Now have a look in the trough underneath the evaporator, and check for ice buil up- there should be no ice in this trough. If it is iced up, you need to defrost ice and then pour some water in the trough and see if it runs away. In the middle of the trough there is a small hole where the water should run down and away to collector tray at rear of fridge- if this hole is blocked, water won't run away, so builds up and freezes and blocks air flow to fridge. If hole is blocked, poke a wire down to unblock.
If in doubt, call in the experts- F+P fridges can be a bit fiddly getting apart, as everything clips together ( I worked for F+P for 10 years, and I still sometimes have problems getting panels off easily!!)
Good Luck!!