You're not unreasonable to put a boundary in place with friends being negative about your choices if you're willing to maintain it - though with the friend making a remark about them being in the same class, I'd likely have just responded with "Maybe," and changed the topic. Even if it's not true in reception, it may be true later on.
The mindset that "Fulltime school isn’t right for our family" is not one I'd recommend at this point. It's one thing where families who've had a child just not get on well with full-time school education, but I've met some home educating families who start from that point, and it made it more difficult when their child needed more academic support to develop later on, often around secondary age. After years of telling themselves that school isn't right for them, it became difficult to make that change for both parents and child. Even when the kids were college age, I've met a few where it's just ingrained in them that school isn't right for them and it cost them dearly in opportunities.
To be honest most home school parents seem to be religious extremists or 'dont want my kids to learn about there them gays' type people so don't blame them for being judgemental
In the US, that is true in many areas, and they produce a lot of online content about starting home education from the start and doing it throughout in a vey structured way with religion involved.
In the UK, it tends to be the opposite - British home education has a lot of unschoolers. Most home educated kids in the UK are withdrawn from school rather than starting that way, so it's from having many issues with schools in an area. Even those who do start, it tends to come from issues finding suitable local schools (particularly for children with additional needs) or parents like the OP who have an issue with schools in a similar way of viewing schools as too restrictive, and they tend to be very open about sexuality and other things as part of that.
I’m not smug about it, but as a pp says, teaching reading, writing a maths skills to a single child with unlimited time and resource is a task I feel prepared for,
There will not be unlimited time and resources. It may feel like it before starting, but there will be a lot that eats into that time, resources, and most importantly - energy. It will not do you or your child any favours to go into it thinking these will be unlimited.
We’re saving as much of my salary as possible to put into a SIPP for me to mitigate this hoping that a large amount compounding will help mitigate years of non-payments.
Why would you have non-payments rather than budgeting for additional, even if lower payments?
OP what will you do if your 4 year old sees their peers going to school, and says they want to go too? Cries as he/she sees the local kids walking past the window on the way to school?
I've four kids, lived on the walking route between two primary schools, regularly walked past one of the primary school while it was in session, and never had this issue.
We’re planning on getting the Lovevery Reading and Maths sets which start at age 3 and builds up to age 7.
That's pricey kit and a lot of parts for something your child might not get on with.
I would recommend considering free and lower cost options before jumping into the all singing all dancing unified packages that has great marketing, but if your kid doesn't get on with it, it's money down the drain and clutter in the house.
There’s a strong HE network so we’ll meet up with other families, go to clubs and team sports, and others as their interests develop.
Have back-up socialisation options. From someone who had kids badly bullied in home education groups - yes it happens - and even as a parent I got repeatedly mocked as a structured home educator in with mostly unschoolers, have back-up socialising options as well as proactively expose your kids to potential interests, including things that don't interest you or your spouse.