There are no current extenuating circumstances or automatic renewals in regards to MoT, despite the lockdown. But you could ring up the garage you have it booked in with and ask if they will drop off and pick up the car for you. I know some places are doing this, Halfords is one.

If you don't get the MOT done, your car won't be considered roadworthy and you'll put yourself at risk of a fine. It would also invalidate your car insurance. If you don't want to - or can't - get the MoT done during the lockdown, you should make a SORN declaration and keep the car on a driveway or private land, as long as it's not on the public highway.