I'm not a WT instructor but routinely fly/train and occasionally coach in UK windtunnels, in particular Basingstoke/Bedford and see a LOT of first timers go through their doors. Apart from the occasional 'kicker' or very awkward individual, the staff are very good at getting first time flyers flying unassisted in their two minutes of time. It is obviously not a position for AFF/FS, but it works and is easily adaptable from there.
300 jumps is all well and good, but 10 years out of the sport definitely forms some cobwebs, especially for a relatively low experience before your break - even a few months off I can feel rusty. Without seeing video, anything could have happened, but rather than building yourself back into flying it sounds like you 'remembered' how to fly but struggled, got stressed out and stopped relaxing with only the world to blame. Everyone is guilty of seeing the red mist when flying and it usually results in a good few minutes of unproductive flying before cooling off. When coaching I will absolutely not ask for the speed up if the student is looking stressed out or potentially unstable/unsafe. For reference if you turned up at a dropzone 10 years out of the sport, you would most certainly be doing some jumps with an instructor - would you be telling them how to fly?
Your comment that the wind tunnel is not recommended at all to experienced skydivers is pretty incorrect to be honest though. The tunnel is a fantastic, safe place to learn new skills and improve your flying. It is no replacement for the sky of course, but the tunnel does allow for skydivers to rapidly repeat skills, while being assisted/spotted by instructors. You don't need to look very hard to see children who have never skydived in their life completly at home in the wind tunnel without ever jumping out of a plane. Please tell me how this is 'not recommended'?
My recommendation to you if you are keen to get back into the sport would be to get hold of a coach, there are loads in the Midlands which I am guessing you are based. Buying time from a coach is almost always cheaper than buying direct through iFly, they are also skydivers which often WT instructors are not so are better at tailoring your flying around you and give you a proper debrief. I am happy to recommend several to you.
In terms of your videos, proflyers at iFly UK tunnels can view their videos in team rooms without having to pay for them for reference.