twice round the block

Cut an inspection hole out of the plaster board. Best to do it now while you still in construction mode.

You should try doing a build near Beaconsfield 💰💰💰💰

Not keen on the brick choice. Why is there a brick pier laying on the ground that was obviously not tied into anything and been pushed over?

What was there before the path was installed? Is the property next to a main road? It looks like the kerb stones have been there a number of year's.

Judging by your description of the property, there may not be much competition with other potential buyers as it could be a step too far for lots of people with the amount of work involved. Is the property currently occupied? What's the state of electrics like? Take your rose tinted glasses off as I think minimum refurbishment cost will be 150k. and go north from there. Is the rest of the family as enthusiastic as you ? and are they willing to learn new skills and take on a 3 year project?

Small mistakes with a digger can result in large amounts of extra concrete and muck away if you've no where to loose it.

Sort out a landscaping plan if you haven't done one already.

Get your totals together and take them to your 4 local big builders merchants and ask them to price it. You may get an even better deal if it's a cash account your running and not a credit account. Some times cheaper is not always best. We had lumpy lime and cement, engineering bricks with hair line cracks in them that couldn't be used for garden wall tops, curved creasing tiles mixed with flat ones. etc. For the next stage of the build for the sake of a few hundred pounds I think I'll be using another merchant, who's goods are top quality and the yard staff and delivery drivers take care in handling YOUR expensive materials ( I have plenty of my own hardcore) I don't need them too create more.

Angle bead only goes back 50mm max from the corners. If you get someone that's careful with an angle grinder and can cut straight lines it would be easy to remove. As @nod said put a cement band around the door and window recesses when removed. Scrape the loose paint off the render, let it dry and treat with a sealer primer. You do not have to remove all the render just the area's where the angle beads are that are rusting.

JCH Groundworks would be a good starting point getting them to quote as they also own grab and tipper lorries, so can do muck away and supply agrigates in bulk which you will need for your drainage work etc. I've found the bigger companies to be more competitive than one man band outfits, plus they can supply crushed concrete, road plannings, screened top soil etc at £260 for a 20t load. which a one man band can't as he will need to put his mark up on it, for arranging everything.

I think most people's gardens look the same that have either compacted sub soil or clay below a thin layer of top soil after the rain we've had in the last couple of month's. My plot has water features that required no excavation or designing.

Outside tap x 2 1 hot and 1 cold.

Should have used Hallhook Slate repair clips. Permanent, invisible and cost less than a blob of mastic sealer.

The slabs are upside down.

You could skim, depends on the thickness your trying to make up. I've used out of date multi finish before as it cures faster ( if it's really out of date it goes off in the bucket ) 🙄