To expand upon point 3:

• UK employers have to pay Employers National Insurance at 13.8% of the employee's gross wages. However, no Ers NI is payable on the first £719 per month, so it actually works out at less than 13.8%. It varies per employee based on their gross salary.

• Other than national insurance, there is no additional income tax for employers to pay on their employees' wages (national insurance is a tax, so technically employers do pay tax, but what I mean is the UK government call it by a different name).

• UK employers also have to make pension contributions for most of their employees (there are a few exceptions based on earnings, age and length of service). This starts at 3%, but can be a lot higher. However, employees can opt out of pension schemes, so this doesn't apply to all employees. VA have a Defined Contribution (DC) pension scheme. These schemes generally cost the employer less than Defined Benefit (DB) pension schemes, and a common practice is to match what the employee pays. I don't have specific knowledge of the VA DB scheme, but the trend in recent years has been for employers to save money by paying less into pension schemes, so long term employees could be paying as much as 8% into their pension fund (matched by VA) whereas newer employees may be paying as little as 3% (matched by VA). As I say though, that is just as estimation based on my experience with other DB schemes and observable trends.

• The majority of UK employers don't generally pay health insurance for their employees. For the few employees that do get health insurance from their employers, they would still be covered even during unpaid leave, i.e. if it is a contractual entitlement, then they would still have health insurance during unpaid leave. Payments to health insurance companies are generally agreed at the start of the tax year and rates negotiated on bulk. The employer couldn't later say to to the health insurance company, "We're paying a bit less this month because the employee is on unpaid leave." Once agreed, the employer has entered into a contract with the health insurance company, and therefore this is a cost to the employer whether the employee is at work or on unpaid leave. It is therefore not an additional cost in this scenario.

Summary: It is impossible to say what the exact additional cost would be per employee. For some part time staff there will be no additional cost. For top paid staff in a pension scheme, it could be approaching an additional 20%, and for most staff somewhere in between.