I've only joined today and have done my best to find some threads on my problems so forgive me if these are old and often discussed issues.
I've brought a 'G' Reg T25 which has a few glitches. I've just spent over £900 getting it through the MOT however, even after that, there are still some issues which I've had from day one and some more problems that have emerged since which I want to fix in order to sell the van (before I get lynched) as I'm afraid the wife and kids can't take the stress of the constant issues

If anyone can help with any of the following I'd be really grateful.
1. No dial lights at all. At night, I can't see what speed I'm going, how much fuel I have etc. Could this be a relay related thing? I first picked the van up in the day and so was not aware of this until the first time I drove it at night.
2. Indicators suddenly stopped working whilst driving to Blackpool last weekend. Not nice! - A relay I think?
3. I suspect a previous owner has tried to fit a buzzer that tells you when you leave your lights on. However, on our van it works the opposite way around which has led to several times where I've left lights on during the day and got a flat battery. Basically, I have to drive around on a sunny day at least with side lights on to get rid of the buzzing sound.
3. I am having to disconnect the battery when not using it for more than a day as something is draining it.
4. This is just a general question (probably a dumb one but hey!) - What is the connection between the starter battery and the leisure battery? Put another way, I disconnected the starter battery once we'd arrived in Blackpool so it wouldn't drain as I thought I'd be able to use the rest of the van from the leisure battery but when I switched the 12V switch to use the internal lights, nothing happened. So I had to reconnect the starter battery which, yes, you guessed it led to a flat battery when it came to leave. Oh the wife was so happy!!! ...........Stupid F@#?ing Van, or something along those lines I think she said!!
5. I know that the previous owner fitted a new stereo. Could this be what has led to some of the above issues?
Really appreciate any advice/help I can get,
Many thanks,
Ian