Having done a little more reading and research, I thought that I'd followup my own request for help with the solution that I've come up with. It seems to largely fall in line with the concept that Alabast has suggested
Whilst Eldarin isn't an ideal race for Warlock I reckon my best bet is to play to the Eldarin strengths and hope that teamwork can make up for his weaknesses.
In my eyes his strengths are:
Bonus to Int and Dex. Extra teleportation per encounter (which goes well with Fey Pact). Extra skill trained (any skill I think, not just extra class skill).
Reckon that I'll go for stats along the lines of the following:
Str 8
Dex 15
Con 15
Int 15
Wis 10
Cha 16
So +3 with main attack is hopefully just enough and +2 with secondaries (Int) that will also increase to +3 at fourth level. A decent con to help off-set the weak fort defence and boost HP.
Why the 15 in dex? Well, with Shadow Walk, Misty Step and [racial] training in the Stealth skill, I should have the potential to be quite an "elusive" striker....again playing to my strengths.
I'll probably multi-class to Wizard, as that would give me an extra encounter power (I'll pick one that targets Fort defence as don't think Warlock has one of those at low levels) and also I'll be trained in the Arcana skill for free (maybe doesn't add much in power levels but perfectly fits in with the character concept).
Skills at level one should be:
Arcana: +9
History: +9
Stealth: +7
Insight: +5
Bluff / Intimidate: +8
+Regional skill training?
Defences at level one:
AC: 14 (ouch)
Fort: 12
Reflex: 13
Will: 14 (+5 more vs charm)
HP: 27
Initiative: +2
Main attack: Eldritch Blast will be +3 vs Reflex for 1d10+3 damage
Looking at that as a whole, and bearing in mind it is a first level character, I think that the AC seems the only real weak spot, although it would be nice to have another +1 or +2 on the main attack.
At level 8 (?) when all stats increase by one, I should notice an improvement. Dex, Con and Cha modifiers should all increase by one, and thus defenses increasing too (with Int increasing at level four).
Anyone got any thoughts on flaws that I might have missed or tweaks that would improve him?