Is a share only worth 0.001p?
No. It is important not to confuse the company's share capital (an accounting term) with its likely market value.
Shares in imutual are classed as 0.001p ordinary shares. 0.001p is not a share price and does not reflect the possible market value of the share. It is common for companies to have this "nominal" share value expressed in pence or fractions of pence. By way of example, shares in Betfair are classed as Ordinary 0.1p shares. Unlike imutual, Betfair is actually quoted on the stockmarket and the share price (i.e. how much investors actually think each share is worth) at the time of writing is £8.80
Another important factor to take into account is how many shares have actually been earned by members. In reality, your "share" of the company is based on that rather than the total number of authorised shares.
For more information on how the company's shares are structured, see How many shares are there in total? and How much are shares worth?