Thanks for the responses guys i really didn't think anyone would care
To add a bit more this is the plan i have in my head, red will be the first bits i'll do, then the blue at some point and lime green would be a nice to have but would require a lot more work so will probably never happen. I have about 180m of 20x10 steel bar which will make 90m of track which will do all the stuff in red, got a load of assorted other steel delivered at the same time for other projects.
The garden is quite steep going from the top where the drive is down to the right hand side as you look at the map, it drops maybe 2.5-3 metres so the gradient will be quite steep which i'm a bit worried about as it'll have a short bit of about 1 in 15 which is extremely steep for a railway but i can't think of any way to lessen it without doing some major civil works. I did some tests the other day by packing some wood under a bit of track and found the engine with 1 wagon full of old car batteries would go up a 1 in 10 slope, as i only have brakes on the engine itself when you get off it did start to slide down the rails. Seemingly a large part of its tractive effort relies on the drivers weight as it weighs about 70-80kg on its own so the drive almost doubles the weight.
Also made a few more fishplates which is how i'm joining the pieces of rail together, there's lots of schools of thought on the best way to do this but this is my solution. They're made out of 20x3mm flat bar with 6mm holes drilled and i'm using M5 bolts with nyloc nuts done up fairly loosely so there's some movement for expansion.
And this is how it looks when fitted
As for other future plans, i need to build some more wagons. I'm not 100% on what i want yet so i'll probably just make it up as i go along, the most expensive bit is the wheels as there just isn't anywhere that is cheap but they are pretty chunky solid bits of steel so they probably can't be made any cheaper, you're looking at around £90-100 ish for a set of 4 wheels then another £30-40 for some bright bar for the axles and bearing & holders, the rest i can knock up out of stuff i have in the garage bar maybe a few sheets of ply or some wooden planks.
Then i'd love to build another loco from scratch myself this time, i really want something with a vintage engine in it like a Lister D as they just sound right to me. My dad has a Ruston & Hornsby PB stationary engine in his garage which he may donate if we can figure out how to mount it as they're longitudinal so might be a bit of a challenge on small track, plus figuring out how to get drive to the wheels in both directions is an interesting problem.
Then maybe a steam engine if i ever win any money as they're bonkers money, you could get a very nice 2nd hand car for the price of a fairly entry level steam engine in this size!
And yeah if any of you are ever on sunny Anglesey when all this nonsense is over you can have a ride