recommend a macro lens please

One of the few things I used to use 1:1 for was slide copying. What sort of macro do you want to do? Remember 1:1 in in the sensor so an object will appear life size on the sensor and therefore much bigger on the screen or printed (unless you print very small )

So a photo of a bee of a fly will fill most of the APS sensor. If you are into such photogarhy then 1:1. If you are, it is likely you will be using some form of extender soon anyway.

Do you want it mainly for macro or as a general lens that can be used for macro? If the former an AF 1:2 might be better. If the latter, a 1:1 MF lens would be best.

The 1:2 lens are much cheapr. The AF 100/3.5 Pentax can be as low as £100

Further on Kim's remarks...

Depth of field suffers proportionately with increased magnification. This results in two issues. First, focusing is a lot more critical. A tripod is a necessity and macro rails recommended.

Second, you have to stop down more to get enough of your subject in focus. Therefore, you need more light, and this needs to be targeted on your subject. That's why there are special ring lights, etc. available for macro.

All of this results in greater commitment to macrophotography. Macro of up to 1:2 may be sufficient for your purposes and avoid some of this expense.

What's my budget? I haven't decided yet. I suppose that I could look at it two ways- buy the cheapest available (manual focus) and try it out. If I really like it then I could upgrade.
Or buy a macro lens that's great for portraits too. I have a 4 and 1 year old so it'd get used a fair bit I'd imagine. I bought a Sigma 20mm f1.3 lens for portraits & indoor/lowlight. Outdoors the 90mm lens would be good and give me more reach that my 17-50mm f2.8 lens. But it's not that cheap.
And I have a few lenses on my wish list; 70-200 f2.8 next hopefully, then either the macro lens or a wide angle. Or I could get the later for about the same price as the 70-200 so have those two first and then the 70-200.
it looks like my next few birthday and Xmas presents are going to continue to be photogrpahy related....

Form what the OP said in his 1st couple of posts I'm really suprised that hardly anyone has pointed to the DA-35mm 2.8 Ltd macro'...

If you go for the Tamron 70-200/2.8 it offers macro focussing. I'm not sure how close it will focus (suspect it's more of a close focus than a true macro) but it might bridge a gap while you save for the dedicated lens?

I'm planning to buy one as I want a fast AF telephoto zoom, the macro will be a bonus.

That's perhaps because many people, except those who have this lens, consider it of limited use for macro work.

I'm not denying it's a very good lens, but whilst most macro newbies start off with flower and other static subjects, it's not long before they notice that flowers attract small bugs, and the 35mm is too wide IMHO.

I think the focal length favoured by the majority of macro shooters is around 100mm.

On the other hand 35mm creates an immersive effect, taking you into the macro world. It's also a versatile focal length for non-macro, so it's a good walkabout prime.

May or may not help, but, first picture is with a A 50mm f1:1.2 Pentax lens at f1.2 at the closest focus I could get, then a Sigma 105 Macro lens wide open at f2.8 and lastly, the Sigma 105 at f11, both at the closest focus I could get.

This should give you and idea of the difference between a normal lens and a macro lens.

If you are keen to do macro, I would go for a specialised Macro lens, not one of the zooms that claim to do 'Macro'. But you pay's your money and you take's your choice.

There are a good number of Pentax Macro lenses out there, from brand new to 30 or more year old ones that will still perform on your new digital SLR , and probably lot's more Non-Pentax that will do as good a job

This might give you an idea of the options / differences ?