"My best advice is to be transparent with your (potential?) employer (assuming you have nothing to hide) and let them know what you do outside of work hours and see if they will amend your contract suitably."
So I'm in this situation at the moment, and I did exactly this. I sought an employment lawyer's advice with my previous contract, any they suggested in future that I do exactly this.
I asked HR/legal for a "background IP form" or "prior list of inventions form" (it goes by different names), so I could list my project and ensure that they approve it.
I revived a blanket response from legal stating that I didn't need such a form because: either my projects fall outside the scope of the clause, in which case I don't need to worry about it, or they fall within the scope of the clause, in which case they are not wavering anything. And finally that it's up to me to judge whether the project fall inside or out of said clause.
Not overly helpful. I've tried to play it safe by getting approval, but it seems to have lead to a dead end. Not sure hiring a lawyer at this point is worth it if the company is entirely unwilling to engage in the standard professional processes.
That sounds like a disappointing attitude from their legal department, but if it's a big company I can see that they don't want to get into those sorts of discussions.
Only you will know the stakes and what you're willing to risk; most judges in the UK are fairly pro-employee and take a dim view of big corporations overreaching their rights (but please don't take this as absolute fact!). If you're not a senior employee and you're doing something like I mentioned in my previous comment (making a game in your spare time), I would personally not worry.
If it's your big idea for your future business and you want to work on it in evenings and weekends, then I would want to be rather more cautious.
"My best advice is to be transparent with your (potential?) employer (assuming you have nothing to hide) and let them know what you do outside of work hours and see if they will amend your contract suitably."
So I'm in this situation at the moment, and I did exactly this. I sought an employment lawyer's advice with my previous contract, any they suggested in future that I do exactly this.
I asked HR/legal for a "background IP form" or "prior list of inventions form" (it goes by different names), so I could list my project and ensure that they approve it.
I revived a blanket response from legal stating that I didn't need such a form because: either my projects fall outside the scope of the clause, in which case I don't need to worry about it, or they fall within the scope of the clause, in which case they are not wavering anything. And finally that it's up to me to judge whether the project fall inside or out of said clause.
Not overly helpful. I've tried to play it safe by getting approval, but it seems to have lead to a dead end. Not sure hiring a lawyer at this point is worth it if the company is entirely unwilling to engage in the standard professional processes.