Are there any cyber related internship positions that I could apply for at EY?

Hi Jasmin, yes we do! Our Cyber team sit under our Tech Consulting Sub Service Line. You can flag your interest in the Cyber team as part of the application
https://www.ey.com/en_uk/careers/students/programmes/graduates/consulting-graduate-programme-options/technology-consulting

Does EY provide accommodation for successful internship candidates?

Hi Jasmin, although we do not offer accommodation, we do provide a list of potential vendors, and offer internships across the UK, so there should be one local to you!

How would you describe the culture at EY and what do you like most about it?

Https://www.ey.com/en_uk/about-us#our-purpose
This provides a good insight.

For me, I really love it, very supportive and also collaborative too, everyone wants to help you succeed

For the internship, does EY classify a UK national as someone from the UK who has lived in the UK for a minimum of 3 years? For clarification, I have British nationality but I have only lived in the UK for the past year

If you have British nationality and are eligible to work in the UK this is fine.