Once you have invested £100k per fund the it does not matter if it subsequently falls below £100k, I don't think there is a minimum for subsequent investment. At the cost of a small transaction charge you can hold Vanguard Index Funds at no cost with Halifax Share Dealing. I have held funds direct with Vangaurd , admin efficiency was not great to be honest and I subsequently sold the holding as part of a realignment of my portfolio. Capital gains tax is applicable to assets sold outside a tax shelter such as a pension or ISA. I would do a bit of googling to research the topic and ask specific questions on the Taxes Board.