Helpful lady on the phone today warned that the sports centre's parking is first come first serve, and with all the events they have on at the same time that we're there, it is unlikely there will be spaces still free by 10am.
I'll enquire tomorrow about options for booking parking at Sophia Gardens pay&display, and Glamorgan Cricket Club. I'll update this post with details. I'll be asking about minibus and car. Those were the helpful lady's suggestions. Please say if you have already enquired, or if you have the inside track on better parking options.
ETA (Fri 4 Nov): I've emailed the council about the P&D, and the cricket club. I'll update this post when I hear back.
ETA (Mon 7 Nov): no responses and no phone answer from officials in the council and cricket club. Happily, Tom has sorted Talybont parking so I'll go with that