OP. A mortgage illustration is not a mortgage in principle.
It’s an idea of what you can get. I’m training to be an advisor.
The mortgage brokers you’ve seen, are they tied to a selection of lenders or can the access every single lender?
The 5% fix for 2 years seems high to me as I’ve recently (this week) agreed a mortgage with default on a 2 yr fix at 3.4%
Early repayment charge is not the same as overpaying.
The early repayment is if you pay the WHOLE balance of the mortgage back early or switch to another lender within the 2 year fix period.
The 10% you can overpay by is 10% of the loan value (excluding interest) so you can work this out and factor it into monthly payments. This means you may also buy yourself some breathing space further down the line (within the 2 year period) should you find you need to underpay for whatever reason. This will be detailed in the mortgage illustration.
You say you’re going with a high street lender? In my experience sometimes a specialist lender who deals with defaults are better (see above 3.4% reference).
If all that’s been produced is an illustration I’d be wary of pinning your hopes on the high street lender.
Find out who else your broker has access to. Also don’t forget to have a discussion over protection.
It’s a bit of a hard talk, but if your DH were to be unable to earn, never work again how long would you be able to sustain your lifestyle etc.
You need cover that will look after the mortgage payments/kids etc should the worst happen.
I’d look at a family income benefit plan and add critical illness to it.