Have you had a look at the Key Posts-namely those that deal with buying shares directly or through a fund, and the ISEQ ETF FAQ? Some of the info may prove useful.
One is weighed according to market cap the other will not be. eg if you buy 2k of the top 10 companies you will have 2k of AIB and 2k of KerryGroup. However if you spend 20 grand on the ETF you will have approx 4k of AIB and 550E of KerryGroup.