Survey issue - Bedroom windows

We have gone sale agreed on a property which was grant planning in 1999 and the construction completed in 2001. The house itself is a lovely 2 storey dormer building (4 bedrooms)

We are in the final stages of mortgage process and bank has completed their valuation just waiting on formal offer from bank.

However just last week we got our pre-purchase survey completed and the surveyor noted that the window sills are too high in all the upstairs bedrooms and that this is in contravention of regulations in relation to fire safety and escape and as such these bedrooms should not be used as or classed as bedrooms. This may have an adverse effect on the value of the property and should be considered. Permanent internal steps should be installed under each window as a possible solution.

However when we checked the cert of compliance it stated the building is exempt from any requirement for the making of a Fire Safety Certificate application by virtue of the fact that they comprise a private dwelling house and are exempt under Section 8, Part 3 of S. l. 305, ( Building control Regulations (1991)

We are very confused at the minute.. does this mean that all the upstairs bedrooms are classed as storage rooms ? and therefore technically we are only buying a 1 bed house ?

would this be enough to walk away from the purchase?

Any help on this would be great!