Dave,
Sorry, I've not tried the Puffin. Just looking at the specification, it looks quite light with an average field of view. There is no mention of phase coating which is typical at this price, without it there will be about 30% less light transmitted than those that have it. That's why I mentioned the Barr & Stroud Sierra above.
One non-phase coated model that I have tried is the Bushnell H2O. It's heavier than the Puffin but has a wider field of view. It seems to be popular starter pair, but when I compared it to other Bushnells the lack of phase coating was obvious in low light. The Opticron Oregon is another possible.
If you are keen to spend as little as possible there is a 10x42 from 7dayshop at £33. I bought one following some positive reports here to keep in the car, though the price was even lower then. Much better than you might expect for the money, but not up to the standard of that Sierra I mentioned.
http://www.7dayshop.com/7dayshop-10...hdGFsb2dzZWFyY2gvcmVzdWx0Lz9xPWJpbm9jdWxhcnM=
If full size porros are too big for you then the best quality views you will get for under £100 will come from reverse porro semi-compacts. These don't need phase coating. The Olympus PCI 8x25 (non-waterproof) is a cracking little pair for around £60. The waterproof Nikon Travellite EX 8x25 is currently £75 at Uttings. Of course the smaller EPs will struggle in low light.
David
PS. Oops, someone on another thread has just pointed out that the 7dayshop model is currently out of stock. Sorry!