@YorkshireFelix Engagement and eye contact is a good start! You can reward him just for looking at you, provided he’ll receive a treat nicely without ragging your hand off! That’s an easy win for him, and a key step which can be built on over and over.
Just some thoughts here – am v much not a trainer and all self-taught but if it was my dog I think this is what I’d do (and I think this is what I did!)
If he won’t walk next to you for a treat without savaging you, have you gone a step too far too soon? First things first, he needs to learn to sit nicely next to you in the heel position (if that’s what you want him to do). Once he’s got that and he isn’t attacking you (!) then you could add in a little shuffle forward, rather than step forward per se, so he’s travelling with you but dead slow. So it would go: shuffle, stop, pip on whistle, ask for sit, mark (my word is ‘yes!’), treat and praise. If the whistle is too much then skip that but while you’re teaching the auto-sit, which is what that is, ideally – that when you stop he stops – it’s a good opportunity to work towards him sitting on one pip, if you’re keen to (eventually) work on the stop whistle.
Then, when he’s got that you stopping when he’s next to you means sit, and that sitting next to you is the right position, then you can move it on. It’s hard from afar without seeing what he’s doing!
(Hopefully some of that is faintly helpful!)
Re videos, this probably isn’t quite what you had in mind but the girl who runs this lovely Instagram account, Sunny, who I know slightly, has been doing little updates with her springer pup – look on the ‘Aila starts’ highlight. You might find those useful just to watch someone else doing it, if you know what I mean. I don’t think she’s done any tutorials as such but her pup is 21 odd weeks now and her heelwork is amazing for such a little one. She’s got another spaniel too who she has chronicled her journey with. She’s a really good follow if you’ve got Instagram.
https://www.instagram.com/thorpecreekspaniels/