Extra dice are always handy for this game, but to be fair this is not the best way to get them. At £9 a pack, that works out at £1.50 each. It works out much better if you buy an additional core set, available for around the £25 mark, which has ALL the counters, range rulers, movement guides AND this set of dice. On top of that you get two TIE fighters and an X-wing fighter as well, each ship would normally cost around £10 -£12 individually. If you bought these separately it would cost you around £40 - £50.
You may not "need" the extra counters etc, but they are handy to have.
In short, buy another core set and get more for your money.