Gold/Silver/Metals

Or buy into a physical gold ETF such as www.etfsecurities.com/retail/uk/en-gb/products/product/etfs-physical-gold-phau-lse

As SteveT says, an ETF (there are lots) is the simple way .. gold, silver, platinum, a mixture .. all available. Depending on your risk appetite, you might want to opt for 'physical' (there is about 5x or 10x the amount of gold 'sold' via ETFs than actually exists!) and ones which don't 'loan' it out for others to sell options on. If it's to protect against the end of civilization, then coins may be good (but don't put them in a piano and forget about them, as someone did .. lots of sovereigns and half sovereigns in fact). Mind you, for end of the world, baked beans and shotgun shells may be more use.

Thank you for the advice. 

Yeah I looked at coins but the effective cost per oz if purchasing in small quantity appears to be very high compared to the actual spot price and there is a further loss when selling it back. Effectively you would need a big market move to be in profit.

James, for iShares is the 0.25% the final figure for costs or are there any other hidden costs? I was looking at some ETFs on Hargreaves Landsdown but the costs seem really steep; for a £5,000 investment the fees over 5 years were coming out at something like £570. 

There could be a board here to just to discuss brokers.  Make sure you go somewhere that doesn't charge you yearly fees (custodial).  Unfortunately brokers tend to alter their fee arrangements every so often.
I would suggest you look at Iweb.

At Fidelity you should pay £0 for the ETF in a dealing account.  Don't forget the dealing fee.
I have such account (on the old fee structure) with a token £1k in Blackrock commodities.  I am charged a service fee (pennies), when I queried this with them they said my SIPP service fees are taken from all accounts.  Sounds like rubbish to me.  My SIPP is 100% ETF/IT so is capped at £45 a year.  Though I've paid £100+ which they are still looking into (and confirmed i'm being overcharged).
Fidelity is a very complex beast!  But still much cheaper then Hargreaves.

I bought some Krugerrands about 17 years ago, and I bought 10 at a time - so about £2,000. (The first 10 I bought were £199 each.) IIRC I paid about a 3% premium to pure gold (which didn't seem that bad to me). The UK coins were more expensive at the time, but were CGT exempt,  but I was sure I would have been under my annual allowance so I stuck with Krugerrands. When I sold them a few years later I managed to sell at small premium to the gold price 0.5-1% so I was very happy with the total transaction costs. (I wish I hadn't sold them all!). The smaller the coin the more expensive it is (per gram). Perhaps because you are buying a single coin the costs are higher, and there will be more KYC/Money laundering type stuff now.

Why do you want to buy metal? If it is to diversify, maybe you should accept that you are at a point were the costs of increasing your diversification outweigh the benefits. If you work out what you are trying to achieve there might be a fund or a combination of two, that might get close to what you want to do. (A daft example perhaps not really a suggestion - a global tracker fund plus some swiss francs in cash?)