[ANDTWENTY]

I'm aware this has been discussed before but I'm struggling to find any resolution anywhere for this fault.

Its a 1997 volvo v40 1.8 manual petrol non-turbo

The problem started just over a week ago when I noticed my car wouldn't idle, it would be very low almost stalling at lights and stuff. I was doing some investigating into what could be causing the idle issue and when I disconnected the maf sensor the car stalled, upon restarting the car it wouldn't start, after a few turns and holding the key it fired up. Ever since then I've had this problem, all the lights come up on the dash but when it goes to portions III theres just a click. This isn't happening every time but seems to be getting more common and I'm starting to worry it won't start at all. I'm wondering if its an issue relating to this or just an extreme coincidence, electrics isn't my strong point hence why I'm asking for help.

A few background things that may be useful:
-- The battery was new only 6 months ago and reads 12.53 volts when sat so this seems to be fine.
-- The alternator is also charging the battery and was replaced 6 months ago too with one from a scrapyard.
-- I have not long replaced the headlights from the phase 1 to the phase 2 ones as my old ones where useless, I'm not sure if this could be related but its worth mentioning.
-- I have checked the earth connections from battery to chassis and chassis to gearbox and the both seem solid and connected.
-- The earth wire seems to go between the solenoid and starter housing but this seems to be fine too and the starter looks like it may have been replaced once upon a time.
-- The signal wire to the solenoid isn't corroded but was a bit dirty.
-- when it does eventually turn over sometimes it struggles almost like the battery is flat when its not, could it be that the battery has not cranking power too it, even though its new?

Hopefully someone has the resolution as I'm starting to get worried and have to drive 3 hours away and 3 hours back this weekend.

Thanks in advance!!