The domestic market is ruined.
The people who have ruined the domestic market are now trying to branch out into the commercial, industrial and more specialist electrical market sectors.
Hopefully they will give up or be stopped by being prosecuted or sued before this actually happens.
TBH, would I re-train to be a spark now, no.
Yes you can earn say £30 per hour, but NOT 40 hours per week 45 weeks per year, unless you have something special to offer, which you are not going to get re-training mid life unless, you already have a specialist transferable skill set that you can reinforce with the electrical installation training.
From reading your posts Modfather, this does not seem to be your situaiton?
To be working full time you would be down on the say £15 per hour, then out of this comes all your overheads, stationary, scam fees, internet, computers, book keeping, accountants fees, companies house fees, if you are a company rather than a sole trader, phones, insurance, tax, vehicle, holiday pay, fuel, training, tools, books, test gear, sick pay, advertising, chasing payments which believe me you WILL have to do, sales calls that you cannot charge for, warranty work that you cannot charge for which could well be the fault of the materials not you, need I go on?
Look at what you earn now, look at putting a business plan together for all the stuff you will need to buy, learn, sort etc. then look at the market, and look at the way into the market, in the domestic sector, this is to start price, that is you need to be cheaper than everyone else until you build up a client base these days, so forget the £15 per hour, and base this plan on say £10 per hour.
That's £370 per week or just over £16k5 pa.
Out of which has to come your costs.
Now, is that such a stunning business to be buying into?