So recently while drifting I got hit on my front fender and wheel. The wheel blew the tyre, buckled and bent 5* away from the rack.

There's now a knock in the steering, have no Idea what has caused it either.

No arms are bent that I can see, so I presume I did something to the rack, but I'm not sure. Has anyone felt a knock in the steering wheel? A little bit of loose play there too. Cheers.

If it got hit hard enough to wreck the wheel and tyre as you seem to be indicating then it is quite likely to have done other damage as well.   Could have bent or partly broken teeth on the rack or even caused damage to the pinion or its bearings.    Certainly needs to be pulled out and examined thoroughly
Take a close look at the steering box mountings and particularly around where the column connects to the pinion.

Tonight my car developed a single knock when the wheel is turned right. I haven't been drifting or anything that could have damaged the steering system. I did notice both my steering boots are rooted and have got replacement parts coming in soon but I don't think thats the cause of the problem. Any other ideas? 

Hi Mat.  Seeing as no one else has said anything.   Extremely difficult to diagnose when not on the spot.
Single knock as you turn from straight ahead toward full lock MAY be a bound up top mount on either side.
You could jack up the whole front to reproduce the sound then spray a little WD40 up in there one side at a time and go for drive to isolate it. 
Some of the older cars are developing a slackness  (slop) in the column too.   The first check for this is very easy.
With steering unlocked and straight ahead (On ground). Turn steering about one third of a turn to the left then about one third to the right while listening and feeling for ANY slackness.   There should be absolutely no slop or binding.
With the tiniest movement of the steering (say three mm at the circumference) both tyres should start to move laterally .
Because the rack boots are broken there will be road grime (SAND) in there. Please do your best to clean it out before fitting the new boots.

Appreciate the response Falcon, Yea it's difficult to explain and impossible to capture on video as there is no way of forcing it to knock it only does it intermittently. When I get some spare time I'll definitely jack it up to do an inspection. I have checked what bolts I can get my hands on and they all seem tight. If I had to explain it I'd say it happens most frequently when the car is going up or down my driveway gutter and sounds like there is a metal piece under tension then just lets go and makes the knock noise, appears to only come from the front right.

There is no slop or binding from the steering so it should all be good. 

I'd like to replace inner and outer tie rods when I do the boots but money and time is preventing that. Oh yea definitely giving the joints a good clean once I have them off and then pack as much grease as I can around them. I'll also replace the P/S fluid but time isn't on my side currently :(

Appreciate the tips. Yea I know its not the rack, I've had cars with sticky and broken racks before, its definitely something in the front left hand side. I've done a basic trouble shoot for most things but it all feels pretty tight. The car has actually stopped doing it for the moment which can be a good and bad thing. I'll probably look into getting new tie rods when I go to do the boots if they aren't too pricey just because I'm there.