Hello Gareth,
Find an airtight container, which your phone can fit comfortably into, and partially fill with dry uncooked rice.
Place some tissue ontop. Place your phone on the tissue. Now Place another tissue over the top, and fill with more rice.
Warning.
Leave some room at the top, so the lid will fit comfortably without squashing your phone.
Now pop the lid on. Make sure it is sealed all the way around.
Leave your phone in the tub for a minimum of 3-4 hour.
The longer you leave your phone in there, the more time the dry uncooked rice will have to absorb the moisture out of your phone.
It works a bit like osmosis.
You want your phone to be in a warm environment. This will help the moisture turn back into water vapour and it will naturally try to distribute itself evenly, and start to leave the phone via the same way it got in.
The Beauty of the rice, is it will keep on absorbing all the water vapour, so your phone will dry out almost completely.
The downside is, until you find out where and how the water vapour is getting in in the first place, this may still keep happening.
Normally phones have an inner silicone sealant to prevent this from happening.
The hydraulic and pneumatic machines which administer sealant onto the phones outer casing joints, aren't always 100% accurate. Some handsets are accidently missed on the quality control checks. A simple reseal will do the trick. But you would have to send your phone back to the phone provider who sold it to you. So long as you did not buy a reconditioned phone, and so long as you have had the phone for under two years, your warranty with either the phone provider, (3-6 months), or the manufacturer, who supplied the phone to your phone provider, (1 year 11 months), will cover most of the repair costs. It will not cover postage or packaging and VAT. So there will be a cost, but it should be minimal.
By the way, if the phone is almost two years old, less than two months to go, you are usually entitled to a free upgrade.
I hope this helps.
Tani