Voting systems in the UK

The voting systems in the UK are a complete mess.
 

We are told regularly that First Past the Post is vital to be retained, but in reality different systems are used for so many other scenarios that sometimes its surprising that FPTP has survived for as long as it has.

From Parliament's own website.

AV - The Alternative Vote is used to elect the majority of chairs of select committees in the House of Commons. The AV is also used for the election of the Lord Speaker and by-elections for hereditary peers.

SV - The Supplementary Vote system is used to elect the Mayor of London and other elected mayors in England and Wales.

STV - The Single Transferable Vote system is used to elect the Deputy Speakers in the House of Commons. STV is also used for electing the Northern Ireland Assembly, local elections in Scotland and Northern Ireland and European Parliament elections in Northern Ireland.

AMS - The Additional Member System is used to elect the Scottish Parliament, the National Assembly for Wales and the London Assembly.

CPL - The Closed Party List system is used to elect Members of the European Parliament, with the exception of Northern Ireland which uses Single Transferable Vote.

FPTP - Everything other than that already described above.

Of course, this is just official systems administered (sometimes indirectly) by Parliament and ignores the systems used for internal elections within parties etc.

I hope that's clear...