Rob
OK here goes with description and issues I had. Photos to follow.
I have a '92 SE
Bits
HD solenoid like this
http://www.ebay.co.uk/itm/Door-or-Boot- ... 35b5fe00cdVolvo S70/C70 switch WITH PLUG AND 5-6" TRAILING 3 WIRES IN PLUG (like this:
http://www.ebay.co.uk/itm/Volvo-V70-S70 ... 1e6c5ed19cOrdinary bike cable and 2 end stops from Halfords or bike shop
Simple relay from Halfords
Coloured wire and black wire
Patience (loads!!)
Fitted solenoid with supplied bracketry to boot lamp bracket, end turned up to "L" shape to take cable end stops. Put actual solenoid in its own clamp at slight angle (wood wedge!) to align with incoming bare end bike cable. See photo.
Lock end: remove rubber bung and slide off retainer to remove lock barrel. Remove latch, careful not to lose bits inside boot lid. Did mine in situ. I fastened a small "L" bracket with 2 holes (a short bit of long strip supplied with solenoid will do) onto the RH screw (aerial side of car). Fasten 2nd end stop to this bracket before fitting to car. Having 2 end stops overcomes lansled's problem of not fixing cable outer.
Also suggest threading the cable outer through boot strengthening box from solenoid end and into end stop by latch lever before refitting "L" bracket assembly. Tape outer cable to end stop to hold in place, then refit lever assembly having first slid cable INNER through lever and part way into outer cable. This part is really fiddly but doable with nimble fingers! I think I tightened LH screw first to lightly clamp "L" bracket over RH hole, then insert RH screw through bracket and latch. Then tighten both full, keeping "L" bracket at right angles to latch plate.
Use bunged access hole and lock barrel hole for finger access. You need slim fingers though!!
Cut outer cable to length keeping as taut as possible, then insert into other cable end stop by solenoid. End stops are slightly adjustable to help tautness. NOW slid inner all the way through and pull tight.
Slide inner cable and solenoid cable through each end of single electrical block connector: (open hole all the way through, not blocked). Only cut these 2 cables once you are fully satisfied it is all working.
The adjustment of how these 2 bits of cable are fastened to each other is critical. When you lower the lid, the distance between the latch and the solenoid SHORTENS, so what was once a tight cable (open lid) goes slack (closed lid). To overcome this, pull the inner brake cable so that the unlocking lever moves half to threequarters of its travel. Then clamp cable tight to solenoid cable and let go. As you close lid, distance will shorten and lever will return to its normal position.
Wiring with relays and operated by Volvo switch should be straight forward, but do use a relay. I fed a lead off +battery lead and attached all earths to earth post near fuel cut off switch. See photo. I located the switch somewhere in the cabin. Photo will show where.
Test with boot open, then lower lid but not closed. Test again. It will be trial and error to get it to work, but provided you do the pre-tensioning of the cable to move the lever you will do it.
Mine is also wired in to the alarm via a spare button of the alarm remote. I have Scorpion alarm fitted last October.
Hope this is clear. Most will be made more clear when I get photos, but including photo of latch internals copied from Alexg who posted this method earlier in this thread.
I have also done an electric fuel flap release: well I did buy the double switch! Will detail this later.
Somehow I feel a Wikilec request coming on.................
I would also like to add that this is not my idea: I picked up on this thread initiated by dapinky and followed up by others, read it through and decided to try it. I didn't want to cut the body, but use the cable system. Very fiddly but worth it. The pretensioning of the lever/cable is critical to getting reliability. I have so far not had any problems with either of the releases.
Good luck
EDITED: to correct failing memory re latch configuration and to acknowledge relevant photo.
La vie passe vite: vivez la avec élan.
Elan SE turbo 1992
Emira 2023
Mercedes Benz C200 estate
Lotus Evija Danish edition
is it easier to put the solenoid further away from the lock? Or closer ? Also was going to use bike brake cable inner to connect but after looking at this thread may try to use a piece of wire coat hanger to connect them. 
all went ok after that 
total cost was about £11 as i got a Fiesta mk4 kit off ebay which had the switch included which is a nice compact unit, will take a couple of pictures tomorrow if i get a chance, can't wait for Donington next year as i'm going to throw they keys in the boot on purpose 
and still be on time for the convoy 
and can get them out 
Many Thanks for the above Post John, excellent info, will await piccys then this looks like the first Mod for the Car, like the sound of the electric Petrol cap release as well 
