Any advice for a P2* newbs

newbie It's all down to the level of risk you are prepared to take. Whilst one site could be ideal for one lender, it may not suit another. The best advice you can get is "Do your homework". Don't blindly accept what is stated on the loan page. Do your research and feel comfortable with the opportunity before lending. Be prepared to loose money and if you don't, it's a bonus. MoneyThing is very new and has attracted a lot of lenders in a short time because of the responsive attitude they have and the good rates of return. There is no secondary market so once invested you need to wait the full term before you get your money back. Wellesley offers lower rates. You don't get to choose your loans with Wellesley. they spread your cash over a range of loans and redo this weekly.

So your exit route is something you need to look hard at - how you get your money out, without losing too much interest, when you've found the right BtL.

Have you considered combining the two, and looking at the House Crowd?

What is appropriate advice depends on your circumstances. So nobody can say whether you're on the right lines just from a list of platforms you either like or dislike, or even if you should be investing in p2p at all.

If you say what you like or dislike about the platforms people can comment on your evaluation.

Ratesetter and Wellesley (mostly) address different asset classes, but otherwise seem to me to be rather similar - relatively low yielding, primary risk is failure of the platform, mainline product illiquid, but with liquid (until they aren't_ products (Monthly Access vs Thirty Day Notice) yielding just a bit more than a Santander current account. So why do you prefer Wellesley to RateSetter?

Another consideration with a lump sum is diversification and speed of lending. For Ratesetter diversification isn't important and you can get a lump lent immediately, similarly Wellesley re-distribute your lump over their whole portfolio. For most of the P2B sites (Funding Circle, Rebuilding Society, Assetz, etc) you would need to use the secondary markets to build a well diversified portfolio, which is OK but generally the deals on the secondary market might not be as good since there's usually a markup. The deal flow on some sites (Saving Stream springs to mind) is just too slow to build a sensible portfolio with a lump sum. For some (House Croud, Thin Cats) the minimum bid rules them out for "smaller" investments. To be honest, I'm not sure why you've ruled out Ratesetter; they have perhaps the highest rates of the "fire and forget" type platforms at the moment, but do watch the exit fees if you think you may need to withdraw early (it's better to invest in the shorter markets than withdraw early from the longer ones so plan carefully). Funding Circle's short term property loans aren't bad either, IMHO (although I think MHO may be a minority one), if you think you may want your capital back within 2-3 years, especially the cashback ones or discounted ones on the secondary market.

Zopa very solid - does what it says on the tin. Might be worth a look at Landbay - they are P2P buy to let mortgages - I have some in their tracker and seems quite liquid - earns interest straight away and withdrawals are processed quickly with no fees...

I'm not in RS.  I started in P2P before they did, so I started with Zopa.  I've taken most of my investment out of Zopa and moved it to the higher-rate, probably higher risk, segment (AC/SS/FS).  But if I were starting in the unsecured personal loan segment of the market now, I think I'd go with RS rather than Z.

Yes, the RS exit fees are something to be aware of, but I don't agree with markr's parenthetical remark above.  AIUI, the exit fees are designed to take away the apparent advantage of investing in longer-term loans and then leaving early.  I.e if you invest in 5-year loans and then exit after three years the fee should be the difference between the 5-year rate and the 3-year rate times three years times the amount withdrawn.  If you need to withdraw everything then you should be no worse off than if you had opted for 3-year loans in the first place.  But if it turns out that at least some of your money does stay invested for the full five years then you will end up better off than if you had been in 3-year loans all the time.

If my understanding of this is wrong, I do hope someone who knows better will set the record straight.

PS.  My understanding seems to be wrong.  See comment immediately below from am.  Note to self:  Restrict comments to subjects about which knowledge is better.

Five bonus points for "parenthetical", grasshopper.