You can get a code reader or a dongle and app for less than £10.

I'd get it checked asap as if its a serious issue you're within your rights to take it back. You may feel that it drives the same but it could be something thats been covered up to get the car sold.

Im not far from Lincoln so message me if you need a hand.

 

I work in Lincoln and have a reader mate, if you get stuck pm me.

 

Also, when the code is read you may get a P number.
I can email you my PSi3 Data Reader instructions in PDF format, that lists all the P codes and what the fault is.......by all means PM me.
Welcome to SN too!

 

get back in touch with the seller straight away and make them aware of the issue. id be asking if there has been any problems with the car or eml,s coming on prior to the sale. you dont say if the car is modified or not as a common fault is fitting decats and not mapping them thus causing the light to come on. decats and cone filters etc mess with the afr,s and will most certainly throw up a cel if not adjusted for. sort it now before you end up stuck with a lemon.