You could probably get a decent electronic piano, full size with weighted keys, on ebay or somewhere like that. It wouldn't have to be ridiculously expensive. If you are anywhere near Edinburgh you can have mine (yamaha p-200) I'm moving soon and want to get rid of it!
i have a yamaha dgx 620 digital piano. it has a graded hammer action (the "weighted" keys mentioned) and also comes with a sustain pedal. i bought mine new on-line from chappell of bond st (google) but you can get them on ebay for around £250. the yamaha dgx 620 is an excellent choice for a beginner imho. experienced musicians will, ime, usually recommend a piano, however, don't forget that if you get a cheap second hand one, you are usually looking at not insignificant tuning and reconditioning costs before it will sound anything like as good as a quality keyboard!
so get the exact spec of the yamaha keyboards lidl are selling, post it on here and let's have a look at the details.