Just one question, is daycare that horrible in the UK?? Here it is common place and I know VERY few people that can live on one income so most kids are in daycare. Mine has been there since she was 6 weeks old (because that is all the time you get off) and she has been an independent strong little girl the whole time. I would dare say it put her ahead as well in her language and social skills. She will be three in February and uses complete sentence, is potty trained (except through the long night), learns new things very easily, can spell a few things, and I credit her daycare with much of this. She learned early that I am her permanant mother and that I have to go to work and this person will be her care giver until I get back.
Some of the issue with your little once is the permanence thing. They think you are leaving, but don't always understand that you are coming back. My girl has no fear of that, we never failed her when she was VERY little, and we haven't yet. I think that it helped, but it might be totally different in the UK, which concerns me since we want another, but I will probably have to work.
As for the sleeping, do what is right for you. We did the cry it out thing at about 6 months. It took 2 days and she was sleeping through. Even at 6 months, she knew how the manipulation worked. We stopped going in, and she gave up and slept. We also put a thing in her crib that attached to the side and you just press the button and it lights up a bit and had music and bubbles in it. That helped as well because if she woke up we heard her, but she could press the button when she was old enough and it turned on and she would go back to sleep. Sometimes just something familiar or comforting helps, mine has the fish and her bear.
Food wise, ours went through the same thing. She only at peas and yogurt for months. It will change though. The food throwing though, we didn't really go through so sorry I can't give any advice on that.
You know what is right for your baby and yourself more than any doctor will tell you. If you try everything else and he won't sleep, you could try the crying thing, depends on how you feel about it. I think the clinging will decrease as he branches out and learns more stuff he can do. Right around a year is a hard time for babies because they are having issues conveying their feelings and are starting to walk and explore, but the openness leads to a bit of clinging at the unknown. Hang in there, it will get better.