I am going to be a Wood Elf and become an Archer alongside a theif/assassin.

Due to the fact there are only 81 perks I need to pick my perks selectively. Any ideas would be much appreciated.

This is my current idea....

Archery - max out perks
Sneak - max out perks
Alchemy - max out perks
Enchanting - max out perks

Now I am considering where else to spend other perks. Shall I bother with smithing for example? or partial smithing. Is illusion worth it as there are so many perks on that tree. Also pickpocketing and lockpicking? One handed and light armour. These are all other trees I am considering before I commit a route. Please help !

Any suggestions alternatives would be cool.

i would get one handed or illusion to deal with enemies in close quarters and illusion is way more fun for that

While there is no correct way to play the game, i have a few suggestions/observations:

1) Very few skills in Skyrim are worth completely maxing out perk-wise. Archery can be done just fine without the time-slow perk, 2 extra perks in critical shot, and the last perk. The critical shot perk is especially unimportant, as critical hits in skyrim dont work nearly as well as one would expect (critical hits are only based off of the base rating of your weapon, not the total damage shown in your inventory, making the added damage relatively low).

Sneak doesnt really need the first perk (Stealth) filled out, 1-2 points in it is enough. As you are an archer, you probably wont need the Assassin's Blade perk. The others are up to you.
Alchemy perks would depend on what you intend on using it for, same with enchanting. For enchanting, the central perk tree is the most important.

2) Getting to lvl 81 isnt really required, and takes a fair amount of work/game time. You can easily beat the game and main quests by lvl 50, and i find by then ive pretty much taken all the perks and skills i need.

3) As for other skills, Light armor, pickpocketing, smithing, illusion and restoration can all be quite handy. Light armor is good because you probably will get hit at some points (Powerful enemies like dragons will one shot you at higher levels and/or difficulties if you do not have any armor rating!), pickpocketing makes picking pockets easier as well as the perk that adds 100 points to your carry weight, smithing for obvious reasons (may make you overpowered depending on how far you go), illusion spells can be very good but not only requires a lot of investment perk wise but also steps on the toes a bit with the sneak skill, and restoration is useful to pretty much any character as well as needing minimal perk investment to be useful.

One handed can be good for an archer as a back up, but i tend to not need it when i play archers. If you want to use it, stick with the first perk (armsman). The lockpicking tree has a reputation for being useless, and as someone who has actually taken perks in it to try it out, i can say the reputation is justified. None of the perks really make enough of a difference to warrant perk investment.

So, an Archer alongside an Assassin huh? My favorite build in Oblivion. I would smith to Windwalker in Light Armor. The Stamina regeneration is nice. As far as Alchemy AND Enchanting, I would just pick one of the two. You can get quite overpowered like that. Unless, that's what you're looking for. Then by all means, go for it. Illusion is also another option. Quiet casting allows your shouts to be silent as well. As posted above, 1 handed is also something I would consider looking into. It can really help out if you're getting gang banged. No need to go for lockpicking. It's easy enough in this game. I've never perked into speech, and I've never had a problem with anything. I usually end up intimidating people due to persuasion not working.

Thanks for you're replies. This helps a lot. I think I was just being a bit OCD of think a fully maxed out tree looks cool.

One Handed, Archery, Sneak and Light Armor are my perks for the exact same race/class you have decided on, not maxed them all out, just picked ones I think are useful.

These are my majors as well. And I'm just an Assassin. Accept I went into Smithing as well. Also, as far as Sneaking goes, Shadow Warrior, the last Sneak perk is kind of pointless. I never found a use for it. But, that does depend on how far into the Sneak tree you plan on going. You don't need to max out any of these trees to make an effective character. I understand OCD. I've restarted my same Assassin 7 times because I wasted a perk or two I feel I didn't need after I got it. BUT, that's why I love this game. You can even waste a few perks and still be effective. Unfortunately since I do have OCD, I couldn't just let it be. So, plan well, think about what you want, and by all means, just have fun. Enjoy.