You'll probably earn more staying in Singapore after taking into account taxes and rent, but as privileged as this sounds life is more about earning as much money as possible. You'll still be earning a decent/comfortable amount so if you'd like to go for the experience of working and living in London, go try it out for the life experience then come back after 2 or 3 years if you don't like it or don't see yourself living there long-term.

You should also consider your options in Singapore when/if you want to return - i.e. if the new role is good for your career. YMMV depending on your practice area.

Cheers.