If you do not know someone to take some starter from (always worth checking face book / gum tree to see if someone can send you one) you can make your own at home: –

Make your own Sourdough Starter – 

1. Mix together 500g of strong white bread flour and 500g  of wholewheat bread flour (you can also make up a kilo of flour using plain flour, just brown or white, a rye flour mix (don’t use just rye on it’s own) it is a little heavy.
2. Fill a bowl or jar half way with warm water and add a 4 tbsp of the flour blend into it. Mix to a batter with no lumps, cover with a tea towel / other breathable material (muslin is good) and leave for 3 days in a cool, shaded spot like a kitchen cupboard.   If after 3 days, it is not bubbling around the sides / surface leave for a day or two more. At this point there should be a dark crust over the starter. Pull back the crust and discard 1/2 of the starter.
3. Add to the starter an equal parts water and flour mix (e.g. if you add 75g of water add 75g of flour). Repeat this (discarding 1/2 of the starter and ‘feeding’ with equal parts water and flour) daily each morning or evening for a week. Once your starter bubbles and rises after each feeding, it is established.
4. If you are going to use your starter daily, keep it out of the fridge and covered with a breathable cloth, discard half your starter daily and add equal parts flour and water to it.
5. If you are planning to use your starter more sporadically, keep it in the fridge  (which slows down the fermentation process) covered with a breathable cloth and feed with equal parts flour and water once a week. 

Starter SOS (after a period of neglect!) 

It is surprisingly hard to kill a sourdough starter.  If there is no mould on it you can generally revive it. If there is mould on it; give up and start again. Usually after a period of neglect it is more typical to have a layer of water at the top (termed ‘hooch’) which can be darkish coloured and very vinegary. This is fine and still completely revivable.

A few tips below: –

• If you are going away, add more water to your starter to make it more sloppy. This will hopefully stop it moulding. This has worked for me even when I have been away for a month.
• Once you are back home, tip out the strong smelling liquid from the top, discard 1/2 of it and feed daily with the 75g flour / water mix until it is healthy again (e.g. rising, bubbling and falling after each feed in a predictable way).
• Once it is bubbling and active return to the fridge and go back to feeding it once a week.

Sharing your starter with others

Split it in half, feed both starters with equal parts flour and water and offer to friends and strangers.

When you want to use your starter to make bread 

Take it from the fridge, discard 3/4 and feed it. Leave it until it bubbles / rises / falls. It is then ready to use!

Bread recipe to follow.