Im going to need to replace some tyres on my disco soon (1995 300tdi) and like the look of the bf goodrich all terrain tyres but the closest match to stock 205 80 16 is a 225 75 16 which is obviously wider and has a 10mm bigger overall diameter, will i need to do anything with the speedo if i go for these tyres and also will there be any problems with rubbing etc running the extra width, i assume not just a case of adjusting the stops yes? and last of all any comments good or bad on these tyres please, cheers guys

If you'll read the owner manual you'll see that there's another stock tyre size, 235/70R16.
225/75 R16 is a 10 mm bigger diameter tyre but that means only a 1.3% increase. Since all the speedometers read 3-5% faster than the actual speed, it means the new tyres will bring the speedo reading a bit closer to the real speed. So no worries.
As for the size vs rubbing you can have up to 245/70R16 with no problems except you might need to adjust the steering stops.

I dont have an owners manual for it hence dont have one to read, interesting on the 235/70/16 as thats then only a 1mm difference, is the manual suggesting that 235/70/16 tyres are acceptable for standard disco steel wheels?

If you don't have the owner's manual then go to http://www.ownerinfo.landrover.com/ and get one. Choose a 1998 Discovery, it's the same thing.

The manual says that the 235/70R16 were used/delivered with the alloy rims. But since the rim geometry is the same there's no reason why there shouldn't be used on steel rims.
This is what I have on my 98 Discovery as the regular set of wheels.

My 1996 3-door Discovery 300Tdi Auto has the original steel rims and was fitted with 205/16 Duelers. I was offered a set 245/70/16 Dunlop SP Trac Grips. Dunlop's web site shows the minimum rim width to be 7J. The steel rims were measured and were in fact 7½J. I bought them, and what a delight. I upped the pressures to 2.0 front and 2.7 back, to prevent the possibility of wallowing. I did high way driving and off road and no problems. The speedometer and odo meter now under reads by 2%, and no tyre chaffing on the wheel arches .

I seem to say this a lot these days (no I am not on commission!) but also check out the Grabber AT2 which is available in the 235/70R16 size.

16" Discovery steel and alloy rims are all the same size - 7x16 - so will be fine with these tyres.

Boro

I run 265/75R16 BFG MT on my Disco ...that is roughly 10% larger in diameter than the stock 29" diameter
The steering stops needs adjusting ...a camel cut to the rear fender ....speedo is 7%under and odo is 10% under.
The biggest problem I have is a loss of power at cruising speeds.

What I am saying:
1-4% larger in diameter I think would not give any problems (your speedo might actually just be spot on and your fuel consumption better)
Up to 245 wide should also not be a problem depending on the profile.

As for BFG AT tyres: I liked them and would recommend them as one of the better brands
What I personally did not like was the profile when seriously deflated for sand driving. (The BFG MT has a good profile)

even with standard size tyres but a more aggressive pattern or if there remoulds, then theyll be slightly bigger than stated, so youll need to do a camal cut especially if running modular wheels