my battery went flat been away for a few weeks my neighbour had a brand new battery put it on dash lights up as norm turn key one click noise dash lights stay on havec goes of for as long as key is turned
im just wondering the battery from neighbour is only 640cca is this enough to crank it over or I should be looking at starter motor I've check connections and fuse 40

If it's a Thor, chances are it's immobilised itself. Any messages on Message Centre, like Keycode Lockout or similar?
Was it locked when battery went flat? Did you have to open with key? Did alarm go off when you put fresh battery on?
Do you have the EKA for it?

its thor not asked for eka code I always leave it unlocked so just jumped in put key in just a click I used sync black box to check sync all ok alarmed didn't go off a few bleeps under seat as I turned key off ive checked to insure gears are in correct position and they are

I do have the eka code no message on dash just norm reset windows etc

Well, you've covered the usual suspects. Assuming the new battery is fully charged it should be capable of spinning the car over. Time to go back to basics. It's possible that the battery cables/ connectors are corroded so when you've moved them to change battery they've gone high resistance. Give everything a good scrub and inspect the cables (power and grounds) where they join connectors, and that all of your ground points are clean.
Try carefully sticking 12v straight onto starter solenoid (the thin brown/ red cable) and see if it turns over. Check that RL16 is throwing as well.

What year P38 is it?

If you have no messages on the dash, and it's not turning over then depending on the engine type will depend on what could be causing it.

Could be a sync problem, or could be a fuse box/relay/starter problem too, but a bit more info would help pinpoint it a bit more..

Its 2000 thor engine vogue 4.6 petrol the battery went flat as I was away tried charging battery no good needed changing anyway car was working fine before this. got brand new battery currently has 14.5 volts showing I never lock the doors turned key in the ignition I got engine disabled pressed key fob turned key only one click dash lights all come on as norm when you turn the key dash still stays light up the heater control screen goes off as key is turned and back on again when I let go the key. On the passenger side somewhere when I remove the key there is 4or5 bleeps from somewhere on passenger side as if the door was open I've checked sny with the black box solution says already sny I have checked fuse 40 its ok I have just tried rl16 with a old relay fuse box is 6 months old and was bought new. it has not asked for eka code and there is no display message on dash. ive tapped the starter with a hammer no joy. next im going to try all the connection as been suggested I cant think of anything else to say

As OB says, test if it is the starter or something more complicated first. Pull the small brown wire off the starter solenoid and connect a bit of wire to the terminal. Touch the other end to the positive of the battery. If the starter doesn't turn, the starter is the problem. If it does, then the problem is elsewhere.

I've had the battery off mine plenty of late due to doing the heads etc, and have found it can be a bit reluctant to recognise the key in the barrel. I pretty much just keep turning it off and on and perhaps pull the key a few times and pressing the button, and it seems to wake up and decide I can play after all fairly quickly.

I'm sure there's a technique to it someone else around here can explain, but whatever it is, it might be worth trying that.

In addition to Gilbertd's reply, did you check fuse 40? (my experience from last week, short in startermotor)

just update changed starter motor all sorted know many thanks for everyone's help

It must be a P38 thing, one thing fails and when you put that right you find something else has failed. But you don't know if it's a separate fault or if what you didn't do the first one right and buggered something else up.

at the minute just seems to be one thing after another

Demoralising isn't it :( but eventually once you've whacked all the moles.... you're back up and running!