If you do not hold prices in you head - it is probably not worth bothering. ALL of these kinds of shops are cheaper on many items than in major supermarkets but just take one product out of scores - possibly hundreds - at Lidls.
In Morrisons my bottle of vinegar (the first example to pop into my mind) cost me just 13p. An equivalent in Lidls was 29p - well over a 100% more expensive!
There are a great many similar in Poundland where it is all too easy to pay above the odds. Such shops bank on your carelessness.The secret to massive savings each and every year is to hold prices in your head and to alternate shopping between types of supermarket.
The more people shop around - the lower prices have to become. CONSUMER POWER benefits us all. Careless shopping punishes us all!
Happy savings!