The tradesperson says the job is bigger than the original quote. What now?

This is the most common source of friction, so it's worth understanding upfront. The tradesperson is allowed to identify additional work, but they must: Stop and discuss it with you before doing the extra work; agree the additional cost with you in writing through the Trady messaging system; not start the extra work until you've confirmed. If extra work was done without your agreement, you don't have to pay for it. If you're not sure, raise a dispute and the 30-day dispute process will work out the proper split based on what was authorised.