Combi Boiler sticky flue fan

I have had problems during the very cold spell of a sticky bearing on the Worcester Bosch Cd24 fan assembly (Sifan 0226-016). The immediate problem meant that as the flue fan would not spin up from cold and so the safety cut-out stops the boiler firing up.
The immediate solution was to spray WD40 on the exposed part of the bearing and spin the fan free. There after that all would be ok for a week until the next cold spell and a repeat of the fault. Throughout the winter I dare say it failed up to 6 times however there have been no problems since. I could replace the fan (£100 !) or try to replace the sticky bearing.

Any advice re bearing/fan/replacemt parts would be appreciated.

 

Thanks for your comment, but will new fan stick in middle of winter? The existing fan has worked every day without problem since the very cold weather. I looks to me more a question of bearing/lubricant not performing at low temperatures. Any guidance on replacing bearings or lubrication would be appreciated.