I don't know much about it so I am hesitant to say if its ok to work through or not BUT you seem to be familiar since you've had it before.

Do you have a foam roller? I'd do a full body foam roll before hand (at 20-30 seconds in each area) or especially the back/hips/legs and I'd do some mobility exercises AND stretching - so both static and dynamic stretching.

I'd try some of this as well:
http://articles.elitefts.com/training-articles/coping-with-sciatica/

and I cannot watch this at work but my google search thought it was relevant http://www.youtube.com/watch?v=n6MW6iGfoB0

The following is my experience, and should not be considered medical advice... not everyone who experiences the same kind of pain has the same cause of the pain, hence the necessity to get a diagnosis and treatment plan from doctors/physios

I've had sciatic problems on and off for many years, including (at its worst) bilateral trapped sciatic nerve and the right femoral nerve also trapped, and I could barely walk.... that was when i used to play ice hockey. I saw a physio who said that ice hockey and skating creates a muscular imbalance between the abs and lower back and this was the cause, and prescribed a set of exercise to correct it, which I'll do from time to time if it starts playing up, but in the last ten years or so it's barely been more than a twinge here and there. Also topical muscle relaxants and anti-inflamatories on theback where the sciatic nerve exits the spinal cord help, because what happens is that this swells up, and compresses the nerve, so you need to get the swelling down to relieve the pressure on the nerve.

What else I've noticed is that back then when it was really bad, it would be much worse after 8 hrs of sitting down at uni, but considerably less bad the day after ice hockey training. Exercise (so long as I'm careful about posture/form/keeping the muscles balanced) has always helped. Since doing heavy lifting, I've found that this has helped keep it away, because it strengthens the muscles in an even and balanced way, i.e. the big compound lifts. My whole entire core, especially my lower back, feels so much stronger, and it's a lot easier to maintain good posture while standing. Isolation exercises can possibly make this kind of thing worse. I also avoid sitting or standing in the same position for long periods, and I have to be careful of my posture while standing or sitting. IMO this kind of problem is more exacerbated by being sedentary than from exercising, as I think a lot of back and joint problems are, as they frequently are due to muscular weakness (an imbalance is due to a weakness, because if they were all as strong as they should be, there'd be no imbalance). BUT it's essential to get a proper diagnosis and treatment plan from a doctor or physio, because some kinds of injury require total rest and exercise can make them much worse (I saw a former team mate of mine do that after a partially fractured vertibrae... she's lucky she didn't end up paralysed...)

Hope some of that helps, if it turns out its a similar kind of thing. And make sure whatever doc/physio you see knows sports medicine, don't let anyone fob you off with "stop all exercise/total rest only" unless they can explain exactly why this is necessary, with reference to what's actually wrong and why exercise can potentially cause further damage.

The following is my experience, and should not be considered medical advice... not everyone who experiences the same kind of pain has the same cause of the pain, hence the necessity to get a diagnosis and treatment plan from doctors/physios

you're correct. I really should see my doctor. I have never seen him at all actually, so it's a good time as any.I don't want to deal with being told not to lift at all every again.

we just moved here, got back with a doctor I use to see last time I lived here, they retired after my first visit back, and have been replaced- haven't seen the new guy yet.)

I do have an appointment with an 'alternative pain management facility' in June for migraines. I am half tempted to just take it up with them instead of my GP.

I really do like doctors! just hate needing to see them.

Hopefully any good doctor will work with you to get you back to your normal activities instead of just telling you to stop!

Any idea if last time it was back related or related to muscle tension (piriformis)?