If you are not doing quantity etching, then throwing the etchant away may be the least expensive alternative.
The two etchants you mention are similar, but differ in significant quantitative aspects. Consider: 1) hydrogen peroxide/HCl; and 2) cupric chloride/HCl.
#1 uses hydrogen peroxide as the source of oxidant. True, it does produce CuCl2 in the end, but the concentrations of CuCl2 are a lot lower than one has when beginning with cupric chloride etchant. It releases gas (mainly oxygen), but you cannot regenerate the peroxide by bubbling air through it. Bubbling air will regenerate CuCl2 (if any CuCl is present), but because its concentration is so low early on, you will need to add hydrogen peroxide and possibly HCl to reuse it. In time and with use, #1 can be converted to #2, but you need to review the typical concentrations of CuCl2 that are used, and you will quickly see that you would have to etch a lot of boards to reach those concentrations. You also need a way to control the "free acid" concentration by adding HCl, as HCl is consumed in the process. Typically, that is done by a titration method.
In #2, the CuCl2 takes the place of peroxide to oxidize the copper on the PCB. #2 does not evolve gas, can be easily regenerated, and lasts a long time (forever). You still have to consider the free acid and CuCl2 concentrations. The latter is easily done with a float hydrometer to measure its specific gravity. If you want to consider that method, it is simpler and quicker to just buy copper oxide (CuO) and make up a solution using one of the available recipes. BTW, it is what I now use, and I would be happy to post my recipe, if you decide to go in that direction.
If you are doing a few boards occasionally, do not want to use ferric chloride, and want to use the peroxide method, then I suggest discarding the etchant between periods of use.
Does the UK restrict sale of CuO? That would be another consideration in your choice of method.
John