Fully-blown end-to-end fibre circuits are as good as it gets.
Not to be confused with Superfast Broadband (FTTC), fibre circuits are uncontended circuits with speeds anywhere from 10Mb/s to 10Gb/s. The circuits provide end-to-end fibre synchronous connections (same upload and download speed) from your local exchange to your premises. No other connection offers the guaranteed speed and service levels of a fully-blown fibre circuit.
EoFTTC (Ethernet Over Fibre-To-The Cabinet) is an excellent business grade internet connection bridging the gap between FTTC and fully-blown end-to-end fibre.
Ethernet First Mile (EFM) is a copper-based Ethernet circuit that bridges the gap between broadband and end-to-end fibre circuits. It is available in two variants, EFM2 & EFM4.