Retaining walls and garden shaping

Questions for some of the landscapers among you.

I'm finally in my new house, on a block of 1230m2 so just under a third of an acre. The garden, of course, is a bloody great tatty mess of weeds, thistles, heavy clay soil and compacted earth.

We're starting off by cutting everything back to ground level, but there are constraints on time and money so I can't do precisely what I'd like to do (level it all, poison it, then rotovate it, then topsoil, then raised beds, then compact between and lay gravel or pavers between raised beds, keep a small area of lawn and so on and so forth) from the outset.

I a few questions re the front garden because I want to sort that out first. (The back garden and side gardens can be a long-term labour of love once our fences have gone up and I'm hidden from the outside world, but the front garden will always be open to the road.) The block is 23.5 metres wide and the house is a 10m setback from the road, so my front garden is basically 23.5 metres wide and 10 metres deep mostly. There's a driveway poured to the right hand side, along with a path that curves from the edge of the driveway to the front door.

The problem is none of the front garden is flat - there was a short, sharp batter at the front of the property, so you have road level, then an area of earth approximately 7 metres from road to cut, with a fall of a half a metre over it, then a drop of around 50-70cms to the level of the house - that's where the site cut happened. Because the soil is heavy clay, the cut itself is stable and forms a mini 'cliff' about three metres from the front door.

I have decided some of what I want to do - I would like a retaining wall in front of the cut - I don't think it needs to be a structural retainer as the cut is not high and the soil is standing of its own accord.

I'm in two minds whether to make the retaining wall a metre high and backfill so the front garden is level and then drops to the house, or keep it at about 70cms and backfill a little so the garden is still a slope. Then there's the question of what to make such a wall from. I want to keep some of the front garden as lawn, and some of it as flower beds, so I'm happy to plant various tumbling creeping things along the top edge that will cascade down over the wall and break up any potential monotony or ugliness.

I don't mind the rustic look, and I have access to most materials - e.g. I could buy large wooden logs, similar to old round telephone poles, and split some in half and stack them behind vertically sunken posts, log-cabin style, as my wall. I'm on heavy clay, which will expand in the wet and shrink in the dry, so I'm not sure a plain brick wall would take the movement.

A wooden solution would be my cheapest option and most easy to source locally (I live 3 minutes from the hardware and garden centre so wouldn't have to pay delivery) but I'm interested to hear feedback on pros, cons, alternatives to wood etc.