Bestinvest says
This is an expensive tracker fund and although it specifically targets the top 100 companies in the UK market, it will largely follow the fortunes of UK market as a whole, as FTSE 100 stocks represent a large portion of the FTSE All Share index. The tracker funds that cover the UK index, generally aim to replicate the FTSE All Share index and there are a number of cheap options available. One of the most cost efficient options is Fidelity Moneybuilder UK Index, which has a total expense ratio of just 0.3%.
Tracker funds have an inherent problem as performance fees reduce the margins on performance. Always check the performance fees against similar products before investing in these types of fund.