James
Think I know how you felt. Had a very similar experience to that in a C152 in Florida last year, flying as PIC with 80hrs TT !!
Got caught under rapidly developing CB's heading west to the coast from Orlando in mid afternoon - and couldn't understand what was happening to the aircraft.
Just concentrated on keeping the wings level on instruments - that's all I had the confidence to do even though the ASI was fluctuating between indicating a stall, and then going toward Vne.
I too am now extra cautious about IMC flying.
Hope not to experience that again, but believe we should be prepared for the unexpected. And thanks to the excellent training that is available in the UK - that should be possible for all PPL's.
rgds