Thanks for all the comments guys. What you are suggesting makes sense. I still think The Arai helmet is a good option for the extra visibility but I agree, it needs to be with the visor. I've ordered myself a pair of prescription Oakleys with straight arms, rather than the hockey stick style arms on most glasses as these will be far easier to take on and off with helmet in position.
You get used to doing it. I've worn glasses for 44 years and can get them behind my ears wearing any helmet.
Blatchat Google Search
You will need a visor in an open top car otherwise the circuit operators will not let you on the circuit.
Simon Maitland - Lotus Seven Club - Trackday Co-Ordinator