With plastic rather than rubber cable the socket wiring may be OK, however 1966 the rules changed for lighting, at that point an earth was required on lights, and with that fuse box, it will not be easy to add RCD protection. There is nothing to say you must upgrade, so as long as the cables are plastic they are unlikely to have degraded to a point needing renewal.
The problem arises when you want to modify or add things, or if some one has already modified or added things, so in the main lights with out earths means no metal fittings or switches and covers over any screws in the switches if back box has been changed from original wood back boxes. No fluorescent lamps as getting a class II fluorescent is near impossible.
Most people want an extra socket here or there, or a chandelier, or a metal back plate to light switch and even fitting a cooker could be a problem if the manufacturer says install to BS7671:2008 or similar.
My dad's house was 1954, so 4 years older than yours, he was proud when he moved in as there was a 13A socket in every room where my grand father only had a 15A socket in hall and landing. So as built 7 x 13A sockets. He had spurs from spurs fuse connection units feeding fuse connection units and by time it was down to me to look after some thing like 7 sockets in every room, so the circuits were grossly over loaded and finding the original socket in the room took some hunting.
Around 2004 I had to do a lot of work in the house due to mother loosing a leg, and we were offered to have a new consumer unit instead of fuse box for £150 as the electrician was doing other work in the house, I told dad yes that's a really good price, Part P was in by then so it was far better to have it done by some one who could certify their own work. When I arrived at the house the poor guy was pulling his hair out as there was no way he could get the RCD to hold in. He had no test gear (makes me wonder if really an electrician) and I went to borrow my sons, there were earth faults galore and he ended up fitting an isolator instead of the RCD promising to return next day, we never saw him again, lucky at that time RCD on all circuits was still not in the rule book, so had to register work with LABC and take over the job.
You are likely to find if an electrician tries to change the consumer unit (CU) he will have the same problem and it's a full rewire or nothing. So if you change nothing likely you will be OK, but to change a single socket or switch or light fitting will likely mean whole rewire.
So you need to plan on whole rewire, but you can likely delay it until you want to start upgrading.
Next door had their house rewired in the 1980's and it may be your house has already been rewired once, houses even in 1978 when our first house was built had just 4 fuses, lights, immersion heater, ring final, and cooker, fact that you have 6 points to it may have been rewired already once.
As to size my house was three bedroom, so even in the 80's three bedroom was 4 fuse. Clearly larger houses would have more fuses, there was a version of that fuse box which could take on 45A fuse, but in the main limited to 32A so forget any ideas of an electric shower.
