Do you have an alkalinity test kit? If so it is simple to determine the actual strength of your acid.
1) Measure 10Kg of water into a container
2) Measure the alkalinity
3) Add 1ml of your acid
4) stir and leave covered for 30 minutes
5) stir again
6) Measure the alkalinity
Hopefully you would have a significant (>50mg/l) change in alkalinity, but if not repeat steps 3-6 again. Once you have those values post them here and I'll run them through my spreadsheet to tell you what the Molarity of the acids is. In fact noting that you are in the Dengie you can probably get away with just 5Kg of water for the test. I have to use 10L, AND, dilute the acid 1 in 10!
Actually, if you do know the strength of the acids, they should be used in conjunction with an alkalinity test kit, even if just after treatment to determine the final alkalinity value.
When I'm diluting acids to 'bench strength' I use 2Molar for HCL and 1Molar for Sulphuric that way the acids have the same neutralising power WRT Alkalinity (sulphuric being diprotic, and hydrochloric being monoprotic)