Err, now, the opposite of within, "without", maybe?

Just google a little history and geography, old fashioned subjects not much in favour at the moment.

See

http://homepage.ntlworld.com/peter.fairweather/docs/StLeonards.htm

and In Bristol, to the north of the city, outside the walls on high ground, nearer to Heaven, stands the church of Bristol's Guardian Angel in the form of the church of 'St Michael on the Mount Without'.

and St Ethelburga-the-Virgin within Bishopsgate, as opposed to Parish & Ward Church of Saint Botolph without Bishopsgate.

and Church of St Martin within Ludgate

So there you have it, the only people I've ever heard using outwith are Scots, whether in the UK or Australia. If I find it written in a document I ask them to correct it!