Reducing condensation in my loft - too easy??

Hello there,   
I have a familiar story:
In the recent [extreme] cold snap, I've experienced increased levels of condensation in my loft space.
The 'Rockwall' insulation on the floor and the timber rafters have been getting very damp (wet!!) - all a bit frightening tbh.

I have the old, bituminous felt under the tiles.  I've noticed two characteristics about this old felt that I believe is making the condensation problem worse, but I think I can do some DIY fixes.....
I'll describe each of the problems with my underfelt, and how I aim to improve the situation:

1. In many places, between the rafters, the top edge of each successive strip of felt has slightly curled back over time (into the loft space) by around 5 - 8 mm.  This, in effect, creates downward-hanging edges from which condensation collects and then drips (onto the floor insulation). 
I plan to cut away these curled edges, perhaps removing ribbons of up to 8mm of felt.  I'll remove as many of these "drip lines" across the loft as I can reach. 

2. The overlap of the successive strips of felt up the roof is quite snug (there's no slack).  This means there's minimal airflow between the strips of felt - unless it's a breezy day.   
I plan to slide discs of foam insulation (cut from lengths of pipe insulation) onto the edges of the felt in order to gently wedge the overlaps apart.  I'll attempt to create scatter of these ventilation gaps across the loft.
What do you think??    Do you foresee any problems with my thinking?

Any advice would be appreciated.
Thanks, Vicky


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