Car wont start without a jumpstart. dash lights flicker on and off when i try to start the car

have the battery load tested as it appears that it will not hold a charge overnight

This is the classic symptom of a bad battery. Your engine requires a lot of power to crank but the little lights in your dash require very little. if the battery is even a little drained it won't crank the engine, but everything else will seem to work fine. Either jumpstart the car (if it starts, then you likely need a new battery) or test the voltage at the battery terminal when trying to start the car. If the voltage drops below 12 volts you need a new battery (or at least a freshly charged one)

Flash key fob

You may have an issue with the starter relay, since the battery seems fine, and jumpstart wouldn't do any good. An excellent way to check is by asking someone to tap on the started with a hammer, while you attempt to start the vehicle. If the car cranks, the problem may be fixable; If not, you may have to replace the starter relay.

It sounds like maybe the starter solenoid is defective, they are prone to this type of problem and your description exactly fits. In order to repair this you must remove the starter from the car and either replace it or repair it with a new solenoid.

you have a problem with your gearbox thermo cutout £65.-- repair

with headlights on, try cranling the engine. I they dim the batt is no good, If they go out, you have a battery connection problem/loose or poor contact on groung(neg) cable. If nothing happens your starter relay is kaput.. Good luck

Battery failed.Or alternator problem.Recharge the battery then try..If red light is sill on when car is running then the alternator needs replacing

Have the battery checked.  You may have heard a fast clicking sound when the lights were flickering, if so it's coming from the starter solenoid.  If the battery is bad, have the voltage regulator and alternator checked also.  A bad voltage regulator or alternator will kill the new battery.    

Try starting with jumper cables, if that works, you can pull the battery out, take it to a auto parts store that will test it for free (most parts stores will do this).  If it's bad, you can put a new battery in and then drive straight to somewhere to have the charging system tested.  

Sounds to be a loose or corroded wire/s at either starter motor or at battery fusible links.
Also check the earth strap (Cable) between engine and bodywork.
Hope this helps, MMP