To simulate the equivalent of contact with oak in a barrel, both during fermentation and maturation, would require very large doses of oak chips. Most commercial wine these days never sees the inside of a barrel anyway and most kits don't include oak chips either.
Much depends on the style of wine being produced and personal taste, but as a general rule, a few grams of chips per gallon of light white wine during fermentation will have a subtle smoothing effect without affecting the flavour as such, whereas a full bodied red would require considerably more for the effect to be evident.
If you want the full benefit of oak, you need a new oak barrel, but at £95 for a 20 litre one, this is clearly a luxury which could prove difficult to justify in the short term and may well not be required to produce good quality red wine from good quality kits. I am only using them to mature wine made from my own fresh grapes, which is a different ball game altogether!