even though your car has failed it's MOT you can still legally drive your car to and from the test centre only.
My friend had a Car off the road for a long time and wasn't sure what to do and he found out that you can go to and from the test centre. You can t have insurance with out tax and you can't get tax without an MOT. So don't worry about driving it as long as its only to the mot test centre you'll be fine. Just keep old of your failed certification just in case you get pulled.