The current aerial on the chimney works fine for the standard 5 channels but can’t do freeview at all so I’m looking at installing my own.
May see what the signal is like in the loft first and if it’s too bad then take it outside.
The how-to side of things is covered by the readers digest DIY manual but I’m not entirely sure on the To Buy list.

Is a 52 element aerial worth £10 more than a 48 element (£12 and £23 repectively)
Do I need a strength meter or can I drag a small tv and freeview receiver up into the loft to check the direction and number of channels recieved etc?
what do i need in the way of connectors for aerial -> splitter then onto 4 TV's?
any other specialist tools needed?

It is currently:
SLx 27884D 48 Element Digital TV Aerial – http://www.amazon.co.uk/SLx-27884D-Element-Digital-Aerial/dp/B000NH8516/ref=pd_bxgy_ce_text_b
Or
BLAKE DMX10WB 52 element wibeband digital aeria – http://www.amazon.co.uk/gp/product/B000NOOPNG?ie=UTF8&tag=kstepo-21&linkCode=as2&camp=1634&creative=6738&creativeASIN=B000NOOPNG

25m PF100 Digital TV/Satelllite Cable – http://www.amazon.co.uk/25m-PF100-Digital-Satelllite-Cable/dp/B0019UXVB0/ref=pd_sim_ce_4

SLx 4 Way Aerial Amplifier with Digtial By-Pass – http://www.amazon.co.uk/exec/obidos/ASIN/B0009D5W0Q/ref=ord_cart_shr?_encoding=UTF8&m=A2ZT1QM4DY6IYR

Philex SLx – 27867R Digital TV Signal Strength Meter – http://www.amazon.co.uk/gp/product/B001GXQUNQ?ie=UTF8&tag=kstepo-21&linkCode=as2&camp=1634&creative=19450&creativeASIN=B001GXQUNQ

10 x TV coaxial connectors – http://www.amazon.co.uk/Tv-Coaxial-Connectors-Pack-5/dp/B001J0N5IO/ref=pd_sim_ce_14

And what are F Twist connectors? http://www.amazon.co.uk/100-Twist-Connectors-CT100-RG6/dp/B0012ML8WE/ref=pd_bxgy_ce_text_b

Email Ton. He works for Grax who supply all this stuff for the trade.

Why can't it do Freeview?

What transmitter do you get your TV from?

what do i need in the way of connectors for aerial -> splitter then onto 4 TV's?

Depends on the splitter/amp
The SLX4 you linked will need standard coax [Belling Lee] plugs – as you've already linked

And what are F Twist connectors?

Screw on coax connectors – would be needed on the meter you linked

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Touch pricey though – TLC are cheaper on some things.

You're prepared to buy a signal meter you'll use once but not stump up for the aerial that'll negate the need for a meter??

25M of cable won't go too far to serve 4 rooms too.

See which way everyone else is pointing their aerial and do that. No need for signal meter.

The DIY TV Aerial shop in Stoke (just up the road from Swinnertons) worked out dearer than a local fitter for me.

And the fitter comes with local knowledge too, which is invaluable. And a guarantee that you will get a working set-up.

Uplink – Looked at the teletext page that supposedly checks your signal and all was ok but when i plugged in a humax reciever/recorder it picked up 3 channels all with very bad signal. I'm 22miles from my transmitter which is right on the edge of its coverage area. I'll be getting more cable as tv's are added to the house so thats ok. I can see i won't be needing the meter then! Still not sure whether the 52 element is worth the extra?

I'd be inclined to check all the cable & connections before replacing the antenna
Ideally they need to be soldered if you can
http://www.satcure.com/tech/tvplugs.htm

Remember it's quite tricky putting an aerial high up on the house outside. I did mine last year and remember leaning from the ladder with the aerial in one hand and a screwdriver/spanner in the other 😕 One slip and your biking/walking days can be over…

I looked at doing it diy after seeing the prices people have paid for installations. Seems i can do it myself for at least half the price. I've got the old brown coax cable which I've read is no help for quality. Hence looking at a new cable and connectors. Thanks for the help uplink!

How much does the local aerial guy want to put up a new one & downlead to 1 TV?
£150?
I'd be tempted to get them to do that, run the cable through the loft & put in a back-to-back connector in a suitable place for your distribution amp
Then you can do that bit as & when you want
Make sure he changes all the cable & bracketry

Last resort for me would be to install an antenna in the roof space, there's just too much interference potential
If it's on the chimney, do not – under any circumstances – remove the old lashing wire/straps or it & you may well be coming down the quick way