We did that for our wedding: my parents live in big house which has been converted into 6 flats and has beautiful gardens: the marquee was on the lawn where the tennis courts used to be 
The marquee company was very reasonable - but this was in Scotland so not sure if that's any help to you. Marquee company also (iirc) brought the chairs and tables.
Got the local council to do the flowers (very reasonably priced) but the following year when my db got married, they went to the flower/fruit market themselves and bought a load of flowers and my mum and aunt made up arrangements themselves, also using flowers from the garden.
I sourced cheap pillar candles for the center pieces.
The chef from the local rugby club did the catering and was very reasonably priced. He did outside catering and sorted his own "ovens" etc.
For my db's wedding my mum made loads of tablet for "favours" I didn't think of doing that
Mum also sorted out the weather by making sure there was a plentiful supply of umbrellas and plastic matting to go through the house to the loo - as a result it was a glorious sunny day! 
I'd recommend factoring in an electrician to make sure there is a safe supply to the marquee.
We bought our wine (cava, red and white wine) and beer (South African Castle) from Oddbins on Sale or Return and got a good deal (had some special bottles for the top table from our own supplies) At the last minute we also got a few bottles of own label malt whisky. There was no bar but plentiful supplies - and people didn't abuse it - too busy dancing 
We had 80 people for a sit down meal plus another 40 in the evening for the ceilidh (which included a supper which my mum made: a South African mild curry) That was 16 years ago and iirc it came to £6000 - but it sounds like it was bigger than you are planning
- and I also had to pay for the hire of the crockery, cutlery and glasses.
When I'm back on a pc and not on the app I could post a photo of the marquee - it was a fabulous afternoon and evening. 

I'd recommend it! 