If the circuit is not protected by a 30ma RCD you do need to fit one.
When you open the switch the rating is generally printed on the back of the switch in raised figures - you may need to undo some of the wires to see this. Don't forget to turn off the supply before opening the switch.
10.5Kw is just on 45A and many switches are rated at 45A so with a 50A MCB feeding it could be considered as needing a 50A switch on the other hand since it only draws 45A the 45A switch could be considered as good enough.
I would say neither is right or wrong and is a personal judgement no two electricians will agree on every point if they think about what they are doing only morons would always agree which likely means they are both good electricians.
But I note screwfix sell a brass switch http://www.screwfix.com/prods/62858/Ele ... &source=aw at £11.47 including Vat so I can't quite see how the £50 price tag is arrived at?
Hey ERICMARK, didn't know you did charity work!!!
pull switch at cost + 15% = approx £20, plus 1 hour @ £30/per = £50!!
Seems about right if already doing other work in same house, to make a special journey to do just that is VERY cheap, considering time to order/get switch, waste @ least half day for one hours work, cost of cert. etc.