Many Festivals have songwriting workshops. Upton (May Day BH) always have one or two. Some are discussion groups, some are have-a-go, some are showcases for the "name". Find one that suits you and get a couple of attendees to talk. Songwriting is often a singleton sport and it helps to get other ideas. You will probably dismiss the ideas but after a year or two you will be amazed to see you have used them - if you can remember where you found to the wheezes.
Try Books if you can find it "How to be a Successfull Songwriter" very cynical and American and out of print. Creative Dreaming by Dr Patricia Garfield PhD (197ish)is worth a read - get them on inter-library loan. I wrote a pamphlet called "the Creative Wordsmiths Toolkit" - email me at digitrad@cresby.com.