Yes you can, simply ask the station for an appeals form no. VT17, you then send the form with a full test fee which must reach the vehicle inspectorates local office (the address of which will be displayed at the test station), within 14 working days of the refusal notice being issued.
If your appeal is successful, the fee or, if appropriate, part of it will be returned to you.
Do not have your vehicle repaired before your appeal is considered. Because any changes to your vehicle - may affect the outcome of the appeal.
Finally find an M.O.T station that welcomes you and encourages you to watch and ask questions, if it fails on welding ask them to mark the failed area with waterproof chalk, get a quote for the repairs, and if it's high get one from elsewhere (but remember to build the cost of a full retest fee into the second quote.
There are M.O.T centres that cut price, but remember nothing is for nothing, and some offer them free if you have a service, but think about it... An M.O.T. done properly will take approximately 3/4 of an hour, that's why it costs as much as it does, so if it's being "given" away with a service... How much is the service costing, or what are you actually getting for your money, all i ask is that you think about it.
An M.O.T. done properly, while not an engineers report is probably the only time a qualified engineer really looks all over your car, so take note of any advisory comments the inspector may make, remember your life or that of some one you love could benefit from that advice.