...In an old house with thick walls, you may find it struggles to go through the walls...
Perhaps in the UK, old homes have thick walls. In Connecticut, USA, my walls are all 2" thick made with planks, lath and plaster.
I've seen this blog prior while looking for information. Some of his links are to items that are no longer sold and also some of the jargon that he uses escapes me. When I said laymen, I meant it.
Plus, the XBee Pro that he uses is awfully expensive at ~$200 a piece!
I was hoping to spend ~$20 a thermo and maybe around $100 for the receiver with temperature displays (total of ~$300 +/-). There are commercial products that are not too far from that that do the same things I am looking for. If it is not feasible by making one, then perhaps buying an assembled product from say, Oregon Scientific, is better worth it.