[Ethereum] Guidance on creating new token with value tied to fiat currency & fixed increases in price (newbie)

You can probably do that using an oracle (see e.g. www.oraclize.it , but others exist) to get ether price in the blockchain.

Note that it seems that you will have your client beeing paid in ether while the crowdfunders will pay in pounds. You want to fix the price in pound, but the volatility of ether could do that you client will either get too much ether (if ether price rises during the crowdfunding) or ot enough.

The only way to avoid that is converting back your client's ether to pounds immediately after getting it, but then there was no point converting pounds to ether in the first place.

The idea of decentralization is that people have their token on their wallet, and you do not have control over it.

However there is some exceptions.

Even if you sell a token on a designated market place, anyone could use it elsewhere and sell the token at the prices he wishes on other market places.

Token in a sense is like real world objects. You cannot force someone to sell something for the price you want in the real life. Even a state cannot durably enforce a fixed exchange rate to its sovreign fiat.

However you could design a smart contract, check zeppelin, where your smart contract has the right to sell for the user with the function transferFrom a precise amount of token. Then you could give a fix price to those.