Don't let EAs check your affordability.
Tell them your budget. Tell them this is the max we want to spend. If they push, tell them you have NO interest whatsoever in taking out a longer mortgage term to get a bigger/better house.
Tell them you already have a mortgage broker, so thanks for the offer of speaking to their broker, but your broker is already very good and you trust them.
The only time they should check if you can afford a house is if you have put an offer in, and only then, they shouldn't be putting you through any sort of systems, they should be asking to see bank statements for proof of deposits, proof that your house is sold STC, etc.
Their brokers with dubious morals are trying to push your affordability because they get a higher commission from the lenders the bigger the mortgage they sell. They shouldn't be doing this. My brokers only ever tell me what is a available to me if I specifically ask. They never suggest ways to borrow even more money. I am not even sure it is legal for them to do that.
The EAs are not actually checking your affordability, they are trying to sell you a service, for which they get kickbacks. It's very underhand that they are telling you this is an affordability check, it's not. People are making money off this. Brokers and EAs.
Also, tell them you have your own conveyencer if they ask. Don't ever use an EA's broker or conveyencer.