Cost to remove old electric immersion heater+ install an instant electric heater?

[DuckyUC]

I recent want to replace my old immersion water heater by a instant electric water heater,
I already bought the instant electric water heater (model DEX12 11.5kw)

I live in Birmingham near new st and get a quote of £89+VAT per hour
Is this charge reasonable? I don't understand why the quote are not per project?

For example if there are good electrician+plumber take 3hours to finish the work,
they get pay less then a bad electrician+plumber which take 9hours to do the job?

 

[DuckyUC]

you will see this on TV soon