Shower Replacement. 8.0kw to 8.5kw

Hi
Looking to replace my old 8kw shower with a new 8.5kw. I have a 40amp breaker on my board and the cable goes directly through the roof space. It is "clipped" to the beams and not covered by any conduit or loft insulation. I think the cable is a 6mm but cant be too sure.  Will this setup be ok to install the 8.5kw?  I have some pics of the cable but cant seem to attach them.  BTW I am not an expert on electrics but rewiring the new shower seems very straightforward

Thanks in advance

Mike

Works out about 35a, would happily sit on a 32a breaker all day long.

would be prudent to have the circuit checked by an electrician, a simple job that should take less than an hour.

Also do you have RCD protection and bonding in place? 

The board was replaced about 5 years ago and it has RCD protection. Sorry, not sure what bonding is? Would a 6mm cable be ok?

2 forums , very similar responses

be fine with a 9.5kw from what you describe

Thanks binky