Shyam, you're allowed to drive a car without an MOT to an authorised MOT garage providing you can prove it's booked in for an MOT.
@dollwithabuyn If that was aimed at me, then sorry, I just was interested for my own sakes what people thought the rules are. I'm just trying to help you get the full picture.
All I'm saying is, I know from experience I have had trouble with Halfords MOT with emissions. They tend not to know what they're doing. However, I can't make that assumption here without evidence. They should have provided you with a readout of those emissions, which would tell me how bad the situation. I find it hard to believe they failed you on emissions and DIDN'T supply you with that document.
If that genuinely is the case, then you need to get onto them about that piece of paper, because without it, they could be telling you a load of rubbish. You could then go to another garage for an MOT and the readouts should be very similar. If they are, then you know that the engine is in need of an overhaul. But if it's not then you could go back to halfords and demand a refund.
As I say, driving a car that is heavy on pollutants is wrong on so many levels, if you obtain monoxide poisoning at the wheel and pass out, you could endanger anothers life. Which really is my concern on the matter, and should be yours too. You don't want that to happen. So I am just associating the gravity of the situation to you.