No it is not on the metric system. it is not even decimalised as they claimed at the time. It is a centigesimal system.

The old system used to be twelve pence = one shilling, twenty shillings = one pound.

The abbreviatioons were L.S.D. for pounds shillings and pence.

From the Latin Libra - Pound (plural Librae), Solidus - shilling(plural solidi) and denarius - penny (Plural denarii).

Rule Britannia, two tanners make a bob,
three make eighteen pence and four make two bob.

Other coins were the farthing which was a quarter of a penny and the halfpenny.

slang -
the penny was a stever - rhyming slag for which was coal heaver. Even today you'll hear people say 'ain't worth a coal'
threepenny bits are rhyming slang for tits.
the sixpence was a sprazie
a shilling was a bob
half a crown was half a tosh but I never heard anyone call a crown a 'tosh'
a crown was a five shilling piece also called a dollar from its value years ago. Rhyming slang an Oxford Scholar or simply an Oxford
A pound is a quid or a onecer.