I have a 2010 diesel Vauxhall Astra it started chugging and I have poor acceleration especially going uphill or when I rev the engine over the 20 on the rev counter, I let the fuel tank go low and I was wondering if this could be the cause?
These symptoms sound like the ECU (the electronics that operate the car's engine) has detected an error or fault of some kind and has gone into "limp home" mode and is restricting the revs on the engine in order to prevent any/further damage.
As to what caused the initial "fault" it's hard to say - running the fuel low is unlikely to do so unless there were contaminants in the fuel that was in the system. The old urban myth of running the tank low sucking "dregs" into the engine and breaking it is just that on modern cars - a myth.
The first thing you need to do is to find out what error codes the ECU has logged. Pretty much any garage should be able to do this for you for a small fee (You could go to a Vauxhall dealer but they will likely charge you quite a lot for it!) or alternatively you can purchase a code reader yourself such as this one and use an app on your preferred flavor of smartphone to read the codes.
Once you know what codes the ECU has logged you can then look to get the problem rectified - sometimes it's a simple as a transitory error that once cleared from the system is done and dusted, other times there is an actual issue that will need addressing by yourself or by a mechanic. If you can get the codes (either yourself or from a garage) then post them here and we'll try and give you some advice on where to go from there.