As networking do you mean installing structured cabling or configuring/setting up networks ?
If you mean installing structured cabling there are many companies that do a City & guilds 3667.
It takes a week to do copper IE Cat 5E / Cat 6 this is unit 1 & 4, and another week if you want to do the fibre optic modules 2 & 3.
Both courses are about £1000
I have done both course's, very good.
There's also the NVQ level 2, think level 3 has been scrapped.
If you want to go down the setting up / configing side do the Comptia Network + course very good intro to networking.
And all the course content is free online, you only then pay about £150 for the exam.
Don't start with the CISCO CCNA, been doing mine for about 8 months now, got my exam next month. Driving me mad LOL.
If you need anymore info give us a shout mate