It depends if the manufacturers recommended bulb was 100W to start with (I expect it won't be?) Many are now in Lumens and it also depends where you want to use them on your car as to whether 100W is legal ie fog lights, position lights, additional fitted lights etc
White lights can only be displayed to show a white light to the front of your car or vehicle (with the exception of reversing lights and interior lights)
I agree with @Reality Check as it is easy to compromise and overload the electric circuitry of computerised components in cars.
As far as I can see there are no restrictions on wattage for main beam headlights
For those endless sleepless nights try reading the Lighting Regulations
The legal situation
The Road Vehicle Lighting Regulations 1989 regulate the situation in the UK. Under these regulations, HID/Gas Discharge/Xenon headlamps are not mentioned and therefore they are not permitted according to the strict letter of the law.
However new vehicles have HID headlamps. This is because they comply with European type approval regulations. The UK cannot refuse to register a vehicle with a European type approval. These approvals relate to ECE Regulation 98 (for the HID headlamps which are tested on a rig in a laboratory) and ECE Regulation 48 (lighting installation on the vehicle).
Great Britain road vehicle lighting regulations
The Statutory Instruments which make up the GB Road Vehicle Lighting Regulations are available on the Legislation website of The Office of Public Sector Information (OPSI) as follows:
Base regulation: The road vehicles lighting regulations 1989: Statutory Instrument (S.I.) 1989 No.1796
As amended by: The Road Vehicles Lighting (Amendment) Regulations 1994: S.I. 1994 No.2280
The road vehicles lighting (amendment) regulations 1996: S.I. 1996 No.3016
The road vehicles lighting (amendment) regulations 2001: S.I. 2001 No.560
The road vehicles lighting (amendment) regulations 2005: S.I. 2005 No.2559
The road vehicles lighting (amendment) regulations 2005: S.I. 2005 No.3169