I've now been to Chelmsford City Racecourse three times. Once years ago when it was Great Leigh's and you had to walk across the racetrack (not very disabled friendly) and twice recently since its been Chelmsford City Racecourse.
I must say that access is really good apart from one area I noticed yesterday which was a bit frustrating but it wasn't a big issue.
On arrival you can show your disabled parking badge to the car park attendants/security and you are allowed in the car park area by the entrance. Spaces aren't marked out so I'd suggest that where possible to park with the disabled occupants car door next to a parked car so you can have a wide enough gap. The car park is not really concrete, it's a bit mud like so when wet be aware of muddy puddles (I misjudged and parked right next to one)
Due to distances, crowds and seating I went with my scooter. On my first visit a lovely gentleman walked us from the car to get our tickets and then opened the doors for us. On our second visit we knew what we were doing and just went about our business.
It is a bit of a steep and long way to the main area, you go down a ramped path, under the racecourse (through a tunnel) and up another ramped pathway. If I was walking I'd find it a bit tiring I think. I did see some golf buggy vehicles so I'm not sure if needed you could ask to be taken on one of these. It may be best to ask ahead of going to check.
When you get to the racecourse you get to an area with picnic tables, food and drink stalls and the parade ring. When I went in August 2016 there were wires going across the main route in covered by a plastic bump thing which was a bit tricky to cross with my scooter, but the second time they had left a gap and covered with with a rubber mat which was much better (I didn't raise this, but a staff member was looking the first time I went and pre warned me and asked if I could manage it, so maybe they raised it. You can go inside the main building where the toilets, bar, restaurants and viewing areas are, this is a raised area but accessible via three (possibly 4) ramps at different points around the building. The main doors at the middle of the building are automatic which is helpful.
The toilets I visited, behind the sports bar, were clean and nicely sized. When I used it yesterday the first time it did have the cleaners mop and bucket but this didn't get in my way and was gone the next time I used it. The disabled toilet door opens onto the male and female doors so you do get some impatient people who still try and get passed while you're reversing out. There is also a disabled toilet by the ticket office but I didn't use that so I can't comment on its accessibility.
The viewing area I went to was outside the automatic double doors right by the finishing line. I've read there is a disabled viewing area but I'm not sure where this is but I was happy where I went. We mostly stayed outside in this area while the races were on and by positioning myself against the railings at the end by the stairs I could easily see the screen and finishing line. There are steps so you can go in front and nearer to the course if you like (about 2 metres closer) if you can manage steps (there are railings to hold onto and the steps during look too steep.)
The only access issue I had was yesterday during the countryside day. They had a craft fair in the marquee and during a gap in the racing my Mother-In-Law asked if we wanted to go and take a look. As we got near I noticed people stepping over a threshold to get in and realised there was no level entrance in and I would have struggled to step over it if I got out my scooter and walked. It didn't look brilliant anyway so I said I'd wait outside. When my mother in law came out she said I hadn't missed much (they were in there seconds)
Regarding placing bets, I did mine on my phone online with Ladbrokes while Lee used another app as I found it easier to select my horses in advance and I didn't have to worry about queuing to get winnings etc (or pronounce some of the horses names!) but my Father in Law places their bets in the inside area and found it easy enough, but the desks were a little too high for wheelchair users, however there are other betting areas outside without desks.
My horse picking method (which won me £46 in total in August and £18 in September) is to pick a Disney sounding horse, one related to a song I like, or one that sounds Irish (my Nan's method).
This is probably the last time I'll go to the racecourse this year as most of the races are now in the evening and it's getting cooler and I struggle with achy legs and feeling the cold so I'll probably wait until Spring/Summer next year.
It's a great day out and really accessible I found, and the staff are really helpful and friendly.