Air Bridge and Pre Boarding

I am travelling to Cuba next year with my disabled Uncle. He can walk but is very slow and infirm. I have requested special assistance but have not heard back. I am looking to see if the flights from Gatwick use Air Bridges or buses as I noticed all the planes on remote stands when at Gatwick this year. Plus if they use pre boarding? If so can this be arranged at Twilight Check in? I realise I could call Virgin but I can't take the hold music!
Many Thanks
Many Thanks