I posted this the other day, if they get them back in stock then this is the best price you'll get the DFA 50/2.8 macro for:

http://www.johnlewis.com/pentax-smc-50mm-f-2-8-d-fa-macro-lens/p1091407

If you want a lens which does double-duty as a macro and general portrait lens then the 35 or 50mm macros are the best bet. Anything longer will severely limit your portrait options. However, in a studio environment (as you mentioned that's where you'll be) you may find that something in between would be a better length, such as the DA 70mm (of course this has no macro capabilities). Sigma made (make??) a 70mm macro lens though I don't know much about it.

Congratulations. Hard to argue to your other half that you need a 400/2.8 to take baby photos - is that how far away you'll be when nappies need to be changed??

I have this lens (and previously owned the manual focus version). It's an excellent lens, though in common with other older Sigma wide angle lenses it suffers from flare if you're not careful, so try to get a copy with the original hood.

Nothing apart from the usual to check, I'm not aware of any problems that affect this lens. Check for fungus, check the AF works OK (it's rather loud) and check that results are good wide open in case of decentring or other optical flaws.

I have the DA 35/2.8 limited lens and it's the best portrait lens I've ever used. However, if you want something longer then the 50mm would be better. I have the A version of that lens and it's very good, though I haven't had it for long and haven't used it for portraits at all.

Three in stock at the moment.

http://www.johnlewis.com/pentax-smc-50mm-f-2-8-d-fa-macro-lens/p1091407

Seems like a very good deal, quite a bit cheaper than SRS. Eight in stock as I type.

https://www.amazon.co.uk/dp/B0043RTLA6/ref=wl_it_dp_o_pd_S_ttl?_encoding=UTF8&colid=2U3H94UDZJIC2&coliid=I3QYQH5S2AVZCN

Same price at John Lewis (three in stock):

http://www.johnlewis.com/pentax-smc-da-18-135mm-f-3-5-5-6-ed-al-if-dc-wr-telepho...

No christmas presents here in Spain until the 6th of January and I doubt there'll be anything photographic as my wife is completely clueless about gear and has this strange notion that I already have too much....

Just as well then that I bought myself the Fujinon 35mm f/1.4 a couple of weeks ago to go with my X-M1 mirrorless camera. It was a revelation for the christmas family get-together - sharp wide open so no need for either flash or super-high ISOs in the dark old house.

Ha ha - seems like your wife has the same method of tidying as mine - hide everything.

I like the reflection photo.

It is full frame compatible. A 50mm macro is a very useful lens to have and I've never encountered one that wasn't super sharp wide open.

Seems to be gone. There's one for £199 in Bath but not as good a bargain. Prices on that website do seem to be quite decent for used gear.