Hi there JLL.
Jargon varies from place to place so I'm not sure what a "co-ordination team" is or who exactly you have involved. Where we are, there is usually a "childrens' development centre" in one of the big hospitals and specialist paediatricians there who assess development. At this stage the first contact is usually with NHS.
Global Developmental Delay is a fairly standard bit of jargon, but it's a bit of a one-size-fits-all diagnosis - it doesn't tell you a cause, and it's absolutely no prediction of severity or how far therapy will help. It's not unusual at this age to get a diagnosis of GDD and then the paediatricians will do some tests to look for an underlying condition. Or they will refer you to the local geneticists to do the same thing. But even if they don't find an underlying cause, they still have a responsibility to give therapy for the symptoms.
The diagnosis is the NHS's responsibility. Therapy is a bit more spread out. Some of it is educational, some of it is NHS and some of it is voluntary sector.
NHS first. You should be referred to a SALT (Speech and Language Therapist) for his speech delay. I think you can self-refer if you can find out who to refer to, though generally the assessing paed would do this. His co-ordination will fall between Physio (eg strengthening exercises) & OT (practical stuff like getting up and down stairs safely) They in turn may refer on to eg Wheelchair Services when he needs a bigger buggy.
Education: I don't know if he's attending nursery or not at the moment. If not, he could be eligible for a thing called "Portage" which is a charity running home based therapy for preschoolers. They will visit eg once a week and teach you exercises and things to do with him. Their waiting lists can be huge; again you can self-refer so get onto that ASAP, with a GDD diagnosis they will come out and assess you, you don't need to wait for more info to come in. I found them invaluable because they know everyone and what you are entitled to and which schools are good etc, quite apart from the therapy itself.
If he's in nursery, every educational setting (including private nursery) should have a person called a "SENCO" who is in charge of making sure all kids with special needs have those needs met. So you need to meet with them and talk through extra support - if he has speech problems he may also have comprehension problems and benefit from a very structured day, for example. But if he is in a setting without prior experience they won't have the faintest idea how to help him so you will have to give them guidance as you get feedback from the other therapists.
Money - your main benefit is DLA - Disability Living Allowance. It's a strange benefit which works on the basis of grading a child's disability by working out what extra care he needs compared to others of his age. Depending on that they pay you a token amount which goes nowhere much against the cost of care and equipment etc etc. But the thing is it is the benefit which entitles you and him to other things - from a blue badge to recognition from Social Services to concessions at Legoland, so worth doing not just for the money. It's a nightmare to claim - huge and depressing form - but there is a definite knack to it and there are people in various organisations who will guide you through it. I hear Cerebra have a good guide on your website.
Um... what else? Brain running dry now, what have I missed, anyone?
If I have one overall piece of advice - keep talking and never ever refuse a referral. Your HV may be useless. But she may send you to your GP. Who may be useless, but he may send you to a paed. Who may be useless, but he may send you to a SALT. And the SALT may give you three simple exercises which transform your Son's speech. Or they may be useless but refer you to the OT .... that's how it goes.
Oh, and plug into somewhere like this - Mumsnet SN I mean - because you will find out 100 times more about all this stuff from people here than any professional you ever meet. We've been there. They (by and large) haven't.
Welcome aboard!