Are there penalties for not meeting regulations?

Breaches of the Health and Safety (First-Aid) Regulations 1981 are dealt with proportionately. Enforcement action could include issuing notices or prosecuting if the circumstances warrant it.

Is annual refresher training a mandatory requirement?

No. It is strongly recommended to employers to help qualified first aiders maintain their basic skills and keep up to date with any changes in first-aid procedures.

UK First Aid at Work Training Courses