If I accelerate the repayments on a variable rate mortgage, e.g. pay an extra 200 pm off the capital thus reduce the term, is it easy to do the opposite in case of hard times?
It depends on the lender. Don't assume that if you have overpaid in the past you can subsequently underpay - if you do not have the permission from your lender to take a payment holiday or reduce your payments it will show up as arrears on the ICB and this will cause you problems with obtaining credit in the future. If you do hit hard times contact your lender before you miss a payment and request a moratorium on payments.