Day if you think about it.
Do TT cap
Open hot tap. Turn off mains
Open cold tap.
Set rads away draining down
Sheet up.
Empty ch headder dregs into DHW cistern. Prop it up with ch cistern so water drains out as much as possible.
Start cutting off lagging and cut up vents. Then remove cold supply then everything else . Put all scrap in small headder. Rubbish and lagging in bigger headder. Put pushfit on outlets. Get down lift out rubbish.
Drain cylinder, while it's draining remove immersion cut out all un needed pipework. Remove cylinder bridge out and blank as req.
Carry out loot rubbish and cylinder. Cuppa.
Remove boiler and clear site for new one . Hang do flue and pipe up. Do gas first so it's cool when u do TT. Fill DHW check for leaks. Fill and vent.
Set TT away. Wire up. Check TT. Run boiler do conny and blow off while boilers getting hot. Clear up. Have lunch. 3pm ish. Commission. Come back next day and do all bits. Drain and refill system.
Don't keep going in and out of loft / work area. When u go to van carry some thing there and something back. Always think 2 steps ahead. Half lads running all over because they can't see what they are doing two moves infront.