Houses built in the 60s should have copper pipes in most cases. Lead is DANGEROUS for more reasons than you want to know, and generally went out in the 50s or earlier, but I understand that it was still used in the 70s in the UK. Lead solder was also used, and if present should be removed. I would check when you start to renovate, and if you have a full survey done before you buy, make sure that is addressed. I mentioned lead pipes because they were more common in older houses., and the older the pipes, the more likely they are contaminated. I think the nature of lead makes them more susceptible to build up of calcium deposits.
Any tank should be periodically drained, especially in older houses, as they can be mold pits. Think of it like a swimming pool that needs to be chlorinated, or a well that needs treatment as ours did in rural Virginia. Sad to say, the tank may need to be replaced, but a good plumber can best advise you on that.
While we are on the subject of lead, older houses can also have lead-based paint, which should be removed or treated so it cannot flake. Ingestion of lead can cause brain damage in small children in particular. Not trying to scare monger, but these are issues you need to be aware of before you buy.