Hi Pauline
I advise all the First Aiders I teach to have the vaccination,
that said an an NHS employee it's a little easier than working for a private
non-NHS firm.
We charge £90 for a full course including titre level testing,
and any boosters that may be required. The lab charge us for each test.
This figure is comparable to our counterparts in the area.
Have you tried your local NHS?? They may do the titre testing
for you for a reasonable price. That said the other option is always to send the
employee to their own GP who should oblige. Even with prescription charges this
will work out cheaper, but some GP's are not so obliging.
hope this helps,
regards,
Glenn
(PS HAPPY EASTER everyone, have a good break 
)