Many PS4 games are on PS Now which is £8.99/month (though CD Keys were doing a yearly pass for £35, not sure if they still are). Might be worth checking what's on there.Didn't realise that myself, thought places like CDKeys were selling PS4 digital games etc.
That changes everything for me. Considering I missed out on the PS4 generation, and mainly want the PS5 on day one to play the backlog, I can't see Sony pricing all their PS4 exclusives at great prices on launch, so I think it'll be the physical version for me, even if it's £100 more.