i have a fig tree in my garden, so when would be the best time to pick the figs off the tree

Pick figs when they begin to droop a little on their individual stems. Leave them as long as possible before they fall off or start splitting for the best flavour!

My mothers fig tree on a south facing wall up here in Northumberland is the variety Brown Turkey. The figs are already quite large and apart from drooping when ripening, they should also change colour slightly and become a slightly brownish green sometimes also splitting a little to reveal the fully ripe pinkish-red pulpy centre.

we have a very young fig plant. Does it need a mate to produce fruit? There are no figs this year... or does it fruit not every year or something?
I've kept it in a pot, terrified it'll take over a flower bed - am I being a little paranoid?
Sorry Pegs for hi-jacking your q a little. Ours is also a brown turkey, btw.

It doesn't need another plant to set the figs and it does fruit every year. It can stay in a pot for a while but it's best planted out. You should restrict the root growth though to get the best from it. Mum and dad dug a hole at the base of the wall 2 x 2 x 2 ft putting a 2x2 paving stone in the bottom and four more to make the walls. This was filled with good top soil and the fig planted into that. The benefits of this are that though the roots are for the most part restricted, making it fruit prolifically, a few roots inevitably escape these confines and the plant gets a little extra nutrients by doing this (at least in the long term).

do the roots not damage the wall tho if they are that close? I know it can become a very large plant.
Or is it not a house wall perhaps?
In town I saw a healthy and very large - widespread - fig outside a public building but it never has any fruit on it. Wondered why?

From what I've been told figs never damage a wall and there are fig trees everywhere planted and trained against the walls of houses. As Fractal says, it is common practice to restrict root growth, though we've never done so and always had lots of figs. The reason many fig trees appear not to set fruit is that trees crop twice a year in warm climates: in the UK you can usually only get the first crop from the 'figlets' which overwinter on the tree (about pea size). These then swell and ripen in mid summer. Trees then set another lot of figs but these won't ripen before the winter. During a cold winter the figlets fall off or die off so it's likely there is no crop at all that year.