reversed polarity

hello
can anybody tell me if a gas boiler and programmer would work atall if there was reversed polarity

i believe there is not enough details to give you an informative reply.

If the live and neutral where reversed in the fused spur going up to the boiler programmer would the programmer still be able to ignite the boiler

Live and neutral are AC, it makes no difference either way.

The only thing that might be a concern is safety.

Unless the system is designed so it doesn't matter which way the live and neutral are connected, i.e. it's class 2 (double insulated) or it use double pole circuit breakers or a fuse in both the live and neutral lines it could be a problem. If all fuses are in the live line only they wouldn't blow if the a live to earth fault occurs which could lead to fire and posible electrocution.

The bottom line is, if you're not sure then don't do it.