Sap the place to live usually comes first. You automatically get a place at your local Grundschule. Special needs may alter this though, but you really need local people to answer your question as an out of state answer will have limited applicability. I'd try the local fb group.
Hackney why don't you want your eldest to do a year of Kindergarten? Is your move permanent? If it is it is worth the investment of a year to get his language skills started before school. You'll almost certainly find a wide range of ages in his school class - in my DD's secondary school class last year the youngest is still 11 and the eldest almost 14. In my DS1's primary school class the eldest turned 10 while several in the class were still 8. We held DS1 back a year (he'd have been the youngest child in the class above - we're a one form entry rural school and yes, I know almost all the kids and when their birthdays are, especially as I was a SAHM when DC1 and 2 were at Kindergarten and the start of primary). We kept him back purely because he was very shy and not very organised - his German is native speaker level. There are 7 other children in his class who were held back (6 boys and one girl) so in fact he isn't anywhere near the oldest in his class despite having been kept back. The one and only thing it affects is the annual state sports competition - they compete by date of birth so that is the one time those who were held back stand out as they are measured against others born in the academic year of their birth. Otherwise nobody gives it a thought. Kids who stay back a year generally do better, not worse.
We are outside Munich, only 40 minutes by train from the centre but I used to be on a facebook expat parents in Munich group and barely recognised the Munich experience as relating to my own, so I am still probably not much help.
However:
- The style of education is more old school with emphasis on homework, fitting in
This is true
and kids with SEN seem to have it tougher than in London.
This is not necessarily true - it depends on your point of view. I used to teach at a London secondary school and IMO being put into mainstream with partial TA support is toucher than going to the special schools here with tiny classes and very high teacher to child ratios. I taught "bottom sets" in London with 20 kids all of whom either had SEN or were EAL and had one TA for 3/4 of lessons. I'd say that was tougher on the kids than a special school here.
However if your child is doing well in mainstream in London then yes, the system here may well be tougher and not a good fit. It very much depends on the child, and the school you are coming from.
In our small village I know 2 children who have thrived at special school, one of whom has been re-integrated into mainstream for year 3 (the special school does years 1 and 2 over 3 years, then the children who they feel are ready go into year 3 of their local primary) and another of whom has stayed at the special school and her parents are happy it is the right school for her. However we also know a boy with HFA (not well, long story but his mother is difficult, and dumped her son on me to look after and disappeared out of contact for several hours without telling me he had HFA and behaviour problems or what to expect/ how to manage him at one point, so the relationship is very hot and cold) who spent 7 months without a school place - so certainly the system was failing him. His mother said he did not cope in a mainstream classroom, which I am absolutely sure is true, but he was then excluded until a place in a specialist school became available. I can't say how that is as he's starting in September. However I don't think that exprience is unknown in the UK either.
Certainly there is less support in mainstream schools for SN, but on the other hand I have heard a lot of good things about our local Förderschulen.
- If you don't speak German as a 6y old, either they send you out of town to a school where they let you in or ask you to repeat a year in kindergarten to get your German up to speed.
I have never heard of a child being sent out of town - if anything out of town schools will be less set up to cope with non native speakers. If the child is 6 another year of immersion at Kindergarten is a far better idea than throwing them in at the deep end at school. Children are expected to be very self reliant at school right from early on, and it would take a very mature, confident child to cope and thrive if thrown in without at least good passive understanding of German.
- If you don't speak German as a 6y old, either they send you out of town to a school where they let you in or ask you to repeat a year in kindergarten to get your German up to speed.