Cylinder heads

Hi. This is my first post here, so please bear with me.
My wife has a '72 MGB GT. It's well sorted and runs very nicely. The body's good and it's a fun car all round, especially since we had a Britax sunroof put in it in the summer.
It isn't converted for lead free petrol though, and while I have a garage about 4 miles away that sells real leaded petrol the hours are restricted and it's over £1 a litre. Sooner or later this source is going to dry up.
Now would be a good time to convert, and while I'm at it I though I might try to get a bit more power at the same time. (It keeps up with traffic, but I was out in my company Peugeot 406 HDI today and a white MGB convertable left me standing. I've been told the head is the first place to look for enhanced power. So can someone tell me
1) Is that true?
2) Any recommendations for people to do the work in Herts, Beds, Bucks
3) The likely cost if a) I fit it, or
b) someone else does.
I throw myself on you expertise folks!

There are some real experts at britishcarforum.com There are close to 3000 british car owners there and you will get a quick answer.
Bob

As well as http://www.mgbexperience.com/phorum/list.php?f=1