So that will certainly work, but you need to watch out for environmental protection i.e. the IP rating. For the SPAL blowers you have ordered, they are IP33 (which equates to protection against basically fingers, and protection against water droplets deflected up to 15° from the vertical). Its the latter quality which is critical.
The upgraded fan setup was rated as IP68 (which is protection against dust and crucially protection against temporary immersion), as you can imagine the fan setup is going to get wet, maybe not quite as wet as the UK during flooding session but still wet. I ended up replacing my upgraded fan setup last summer (a symptom ultimately of PEM connector failure), the replacement fan unit was about $180 and I fitted it in 30 minutes. I'd suggest you might consider that flavour of fan long term, I can point you in the direction of the UK stockist who are very helpful.
As for performance with a new PEM (remanufactured EU version apparently), and the new fan unit, I rarely see PEM temperatures above 40C - this morning I ragged the Roadster to Oxford and back (60 miles) in performance mode - ambient temperature was 6°C, and I was averaging 80mph, PEM stayed below 40°C happily.
