Best way to connect new LED light to existing wiring

Couple weeks ago I noticed that one of the four LED uplights in the garden was flickering when turned on (its an ML Accessories / Knightsbridge unit). It would eventually stabilise and work as normal but as the unit is still under warranty I thought it would be worth replacing it.

After some basic safety checks to ensure the electricity to that circuit is off, I lifted the old LED light out and disconnected the cable  from the back of the unit, leaving it in the hole.

The problem is that whoever installed the LED previously, didn't leave a very long run of cable at all. When I was lifting the old unit out, the cable was very taught with the LED barely out of the hole. As such, I can only really connect the new fitting onto the old wiring as it were.

What is best way to do this?

1. I could try to solder new to the old, then put silicone grease and shrink heat tubing around the L, N, E wires, but it would be a major hassle due to difficult access and not enough original cable length

2. My other thought was a 3a connector strip wrapped to death in isolation tape, connecting new and old?

3. Crimp and bullet connector connection

4. Other method? 

I have never seen a ground light that you could disconnect like you have. They are normally  sealed units with a long lead. 

Anyhow i hate those  things, they will let water in and blow, its just when.  I try to talk customers out of using them and ask them to supply the items if they are still want them. I  will get an signed letter confirming they know the risks and costs in repair.

 Solder and  adhesive heat shrink is how i would do the repair but nothing lasts

It's not the best photo but if you look carefully at the second image, you will see that the cabling is protruding from a black connection gland like in the picture attached. This connected into the back of the old light fitting. When I was lifting it out, the gland and wiring detached itself because it was so taught (previous installer didn't leave any lose cable). 

I did think about stripping the wiring from the replacement unit out and connecting up to the old wiring directly, but in terms of future maintenance it would be a pain, that is why I want to attach old wiring to new. 

The new LED has the long lead which you describe. 

That sort of gland doesn't grip very tightly. You could spray a bit of  silicone oil down and gently pull to see if there  is any spare length below.

If it comes from a conduit or similar there may be, but if it's just in the ground there likely won't be.

Thanks for the advice, Geoff. I am a little nervous of giving it a good tug (!) because if it is connected to, say, one of these (attached pic) too much of a tug and it might rip. And since the patio is granite, lifting that up would be a complete nightmare which I'd like to avoid!

Heatshrink crimps is the way forwards BUT it will be a pain

as for it being an ML product...good luck with that one  

you will do well if they even  replace it.

be prepared for years of pain as the others fail,one by one!

sorry, but that's just the way it is with them  

solder sleeves should work well in that position, then overwrap with glue lined heat shrink or Neoprene rubber tape.. If push comes to shove taking a single pving block out isn't usually too much trouble - carefully remove mortar from around the block and it should lift out after a gentle tap or 3 with a mallet

Thank you for the advice guys. I fitted some ML / Knightsbridge dimmers, sockets and switches and so far they have been ok. They carry a 15 year guarantee. The LED light I purchased from TLC Electrical, I am a regular there and they guys said bring the old one that doesn't work back no problems. Are ML / Knightsbridge that bad? The other 3 seem to be ok, although only installed a year ago.

What might be the issue? When I lifted the old one out, there was no water and while soil in the hole was slightly damp, it wasn't touching any part of the LED itself.

ML / Knightsbridge supply "outdoor" cable with many of their lights BUT the quality of the cable is very sub standard and will fail ........................ 

Doh! Wish I'd known earlier. I guess I judged a book by its cover. It seemed decent stuff, price was fair, stocked by TLC Electrical which are popular with the trade and I have always had excellent service there. Fingers crossed the other 3 don't fail any time soon?

Looks like I will go with the heatshrink crimps. Fingers crossed!

Get adhesive/glue lined heat shrink and also wrap in self amalgamating tape, not insulation tape