“Surely his employer should be fined heavily for using an uninsured driver”
Yes his employer could certainly face a charge of “allowing” the vehicle to be used uninsured (though that does not seem to have been the case here). However, unless his employer was a named individual, the “totting up” situation would not arise. In the case of companies or organisations (rather than individuals) being convicted of motoring offences no penalty points can be awarded.
“surely any crim on being sent to prison could claim it will cause "exceptional hardship" for their family”
Be careful what you wish for, baz:
http://www.telegraph.co.uk/news/uknews/law-and-order/10562359/Drug-dealing-father-of-22-spared-jail-to-care-for-son.html
“But a judge suspended the sentence after learning that he needed to help his 26-year-old girlfriend, Emma McNeil, look after their seven-month-old baby, Barry. “