I'll use a combination of circular saw and a reciprocating saw to get through them, a chainsaw would be ideal. They are fairly soft (the exposed side is pretty crumbly) but thick enough to last for years (250mm x 150mm x 2.6m).
I'll get a load of Timberlok bolts from Ebay next.
As for doing things by half, well, we've been here 15 years and there's no reason to move. We're lucky to have a fairly large, and relatively unused, "spare" section of SW-facing garden and my wife has "green-fingers". It's not really about money as such as it will take years, if ever, to recoup any outlay, more about the principle. We want to eat seasonally and be less dependant. This seems a perfect way of doing it.
The long-term plan (I don't want to wish my life away) is a Hectare or so in SW France but life can sometimes scupper long-term plans so we thought we'd have a crack at it now.
Next year we should have 4 deep beds, 2.6m x 1.3m. We've already got some spuds planted in deep soil containers and raspberrys bushes planted. Not exactly self-sufficiency scale but I intend to savour every mouthful next year.
The Wendy-House may turn into a greenhouse yet (ironic because there used to be a Greenhouse there but we didn't know what to do with so many Tomatoes at the time).