Hi, DD has Down Syndrome (so severe GDD incl. mobility & speech). She's been at mainstream nursery part time since she was 1. We've had portage and then EYI officer since she was about 6 months old.
We've been really lucky that the nursery (part of a national chain) has been fantastic and have allocated her additional help, often at their own cost. She's moved up the room slower (was about 1.5 yrs when she went to 1-2 yr old room.
I had been speaking with the Ed. Psych since DD was 1 yrs old about statements, but she advised against applying until DD was 2.5 yrs, as requests before then tend to be declined. Instead she recommended applying for an 'LEA inclusion grant', as these are simpler and quicker to apply for (it was the nursery who applied rather than us)
At 2.8 yrs old, DD is only just starting to walk. When DD moved up to the 2-3 yr old room the nursery applied for an inclusion grant to help fund 1-1 care; the reason they gave for requesting the fund was that DD needed to be in an age appropriate room to help aid her development, but in order for this to happen she needed 1-1 care to keep her safe in this environment. The process is really quick, they got the money within about a week (but that might be because the LEA EYI officer & Ed. Psych. was already heavily involved with DD)
We started the statement process when DD was 2.5 yrs and we should get their decision tomorrow on whether DD gets a statement. If you do go the statement route it takes about 3 months, if all goes smoothly (I.e. they agree to your initial request to assess).
HTH & good luck!