Another thing worth noting, a Ltd company is not really that tax efficient.
Say you expect £50k pa as a salaried engineer. The PAYE after tax take is around £37k and a Ltd company might net you £40k ... figures from memory, but it wasn't as much of a difference as I expected.
From that £3k you need to pay an accountant (£800 ~ £1500/year), deal with administration hassles, buy the insurance policies and risk IR35 non compliance, all while getting no employee rights or easy redress in the case of non-payment.
There are some additional benefits - you can write off business purchases, like software, but then again employers would generally purchase that for you anyway. You can claim back mileage for use of a personal vehicle, but not if to a single place of work (there are exceptions for the first year I believe.) Also, you can hold an annual party not costing more than £150 per employee tax-free.
The reason contracting is so attractive to companies is they can "sack" you with little notice (one contact I saw was 7 days notice.) If you're financially secure that's not an issue, but if you're expecting the reliability of a monthly paycheque then it's not the way forward. The other benefit is the contracting company doesn't pay 13% NI employers' tax, which is the main reason that HMRC are going after contracting firms as they see this as a tax dodge even though the contractor will be usually paying a similar rate to a salaried employee.
Speak to an accountant for proper advice, this does not construe any accountancy/tax/legal advice.