I asked about cancelling an application at the weekend and was told: To cancel you need to apply in writing, wait up to 10 days for that letter to be added to the system, then wait up to a further two weeks for old passport to be returned. They are probably providing worse case time scales but I would imagine your current application approval would beat the old passport being returned. According to Twitter approvals are currently being received for docs received around 7th/8th September.
It’s stressful isn’t it, I am still waiting for my son’s renewal, struggling to think about anything else!