Do I nee to have the fuse board replaced?

It depends on various factors, does your fuseboard have rcd protection 30mA, Is there any spare ways etc, depending on age of property your earth bonding may need upgrading as well. Electrical works in a bathroom is notifiable work to your local building control and should be carried out by a qualified electrician who is a member of a self certification body, who can issue you with the building control notification and electrical installation certificate on completion of works. Get an electrician to quote for the electrical works and he will explain to you exactly what work is required.

Sounds like you need electrician. If you are doing full renovation then rewire ect updating your electrics will benefit you on resale more than any other work. I can't let you know about consumer unit as I need more information.

Any electrics in a bathroom require the protection of a 30mA RCD or RCBO. If your consumer has not got an RCD which can provide the protection you might be able to get an RCBO that fits your consumer. I always recommend getting a few quotes and seeing what each electrician suggests. If one is trying to hoodwink you then another electrician should be able to let you know. Goodluck.

Get an electrician round to do you a survey of your existing system. Any decent one will give you options, and prices of each option. At the end of the day the work has to be done safely and in compliance with the regulations for the certificate you need to be issued.

Consult a qualified Electrician. The builder may have some Electrical knowledge but could also be putting fear into yourself and other clients. If you’re current consumer unit has no 30mA RCD protection in place and installing new circuits to the bathroom then a separate RCD protected unit could be installed for bathroom circuits only, long term would be better changing the consumer unit to RCD protected. An EICR should be carried out prior to any consumer unit upgrade, this would highlight any deterioration within the Electrical system already in place.