Online Health and Safety Courses

Yes it is.
The Health and Safety at Work etc Act 1974 compels employers with the following duty:

the provision of such information, instruction, training and supervision as is necessary to ensure, so far as is reasonably practicable, the health and safety at work of his employees
Part 1, Section 2, 2(c)

Furthermore, The Management of Health and Safety at Work Regulations 1999 identifies situations where health and safety training is particularly important:

(2) Every employer shall ensure that his employees are provided with adequate health and safety training—
(a) on their being recruited into the employer’s undertaking; and
(b) on their being exposed to new or increased risks because of—
(i) their being transferred or given a change of responsibilities within the employer’s undertaking,
(ii) the introduction of new work equipment into or a change respecting work equipment already in use within the employer’s undertaking,
(iii) the introduction of new technology into the employer’s undertaking, or
(iv) the introduction of a new system of work into or a change respecting a system of work already in use within the employer’s undertaking.
Regulation 13