jno is correct, but it is a very confusing area.
You will not be logged with the CRB (Criminal Records Bureau) but you will be logged with the PNC (Police National Computer).
When the police, port authorities, customs etc do a CRB check they go through the PNC which will show a record where your details and that of the offence will be fully logged. Other private companies, such as work checks will only use the CRB, where you will not be known.
But to answer your last point YES IT IS SERIOUS!!!. You are a thief. You could have received 7 years in gaol (in theory). You stole which puts the prices up for every decent person in the UK, not to mention wasting hours of the police time and incrasing shop insurance.
I suggest England do not want you if that is how you respect our country!!!! Stay away you thieving Italian chav.