Low Cost Tracker (via H&L)

I'd advise against your overall strategy but if you want an all world tracker the cheapest two are VWRL (vanguard all world) and SWDA (I shares all world).  The vanguard one includes emerging markets.

If you want a fund then one of the vanguard life strategy funds.

It is not inconceivable that shares could drop 20 - 50% over the time frame you are suggesting, so you better be willing to stick by your "might leave it for long term" should that happen.

I am basically looking for a short term strategy, which could turn into the long term strategy, if it was not favorable to transfer it at the desired time

I was thinking to keep the costs low, so I thought a tracker, due to the low costs

Also I was trying to target better than cash returns, so something above a few % is acceptable 

I'm with hazellend in thinking that 6 months is way too short a timeframe to risk sticking it in equities, unless you're happy to risk a sharp correction (-20%? -30%?) in the meantime.

I wouldn't take equity market risk unless you're able to leave it there for 5 years...at which point the dividend income stands a chance of making up for a market correction.  Nobody knows when the markets will reverse, but given the run we've had a correction is more likely than it was 6 months ago (apologies for stating the bleedin' obvious). 

I am a fan of equities for the longer-term, and have far more invested in equity markets than in P2P, but they are not appropriate if you need your money back in 6 months time and want to sleep well.

There are plenty of options that allow you to keep your money invested in securities without taking the outright market risk of a stock market tracker.

I presume you've already discounted all the fixed income options (corporate bond funds, high yield etc) so we'll skip those - although there are still some interesting corporate bonds out there despite the risk of rates rising- the WASPS bond secured on the Ricoh stadium is one I am familiar with.

Then there's the various listed vehicles that invest in mortgage debt & similar(i.e.they pay the interest out as dividends):
- ICG Longbow (LBOW, managed by Intermediate Capital  Group, only invests in senior)
- Starwood European Real Estate Finance(SWEF, senior & mezzanine loans, so higher risk)
- Real Estate Credit Investments (equity RECI, pref RECP)

Then there's stuff like the student accommodation funds - Empire Student Property (ESP) comes to mind.

You could also look at the more conservative "wealth preservation" investment trusts.  The Rothschild investment trust (RIT Capital Partners) is perhaps the best known, but there are many others.

If you want a bit more fun then some of the more solid dividend yield shares could be considered - utilities such as National Grid & Pennon, although most of the traditionally "safer" shares are far from cheap relative to historic norms.

None of these are recommendations - just places to start your own research.  QE has ramped up asset values for all yielding assets - bonds, property, equity dividends - so correlation is high and they may all come back down at once if the proverbial hits the fan - but you have some influence over whether you lose 15% or 50%.

On the other hand sitting there in cash as inflation picks up will generate a certain loss in real terms, so all risk is relative.

Depending on your investment size, I'd also suggest looking into a Robo-advisor such as Moneyfarm (fee-free for up to £10k + some handy quidco cashback). Nutmeg do the same, although not fee free. Charges are probably comparable with H+L.  As everyone else has said though, 6-8 months is not a suitable time-frame, especially given the bull market.

One other thing, you might want to look into the Halifax Sharedealing service if you DIY. Think it's still just a flat £12.50 per year for an ISA, whilst % charges on providers such as H+L can really mount up depending on the size of your portfolio.

I personally avoid ETFs unless I can find no other way of implementing my investment view.

Counterparty risk is a major problem, although the devil is in the detail and there are many different flavours.  Synthetic ETFs are particularly problematic - you have derivative counterparties to consider, not to mention that the cash you invested to fund the position is often sitting there in a bank - so you find you have an investment with an overlay of bank default risk (and the bank risk can often be heavily correlated with the risk of the underlying investment).  Yes, segregated client accounts should help, but nothing is foolproof when a bank goes under. 

ETFs have their place and the liquidity can be attractive, but there's no extra reward to compensate for the additional counterparty risk.  In some ways you are safer expressing the same view via a leveraged route such as a CFD or spread bet - that way you avoid inadvertently putting lots of cash on deposit at a bank you may not like..... 

Again - these are my personal views and I am not recommending that you start spread betting!