The LUCAS 17TN is available in four frequencies and many different versions.  If you open it up you will see that the PCB part numbers vary from LUCAS TXA through TXB, TXC and TXD (I think).  I do not know what the different versions mean, but I think they all should work.  The frequency is designed to fit in with the overall bandwidth allocation in the target country, as shown below:
 

224.5 MHz	315.0 MHz	418 MHz	433.9 MHz
FRANCE	REST OF THE WORLD including ITALY, AUSTRALIA, JAPAN, US, CANADA	UK-IRELAND  changed to Europe 433.9mhz after 1995	EUROPE  but not France or Italy

It is probably obvious that the LUCAS 10AS is also available in four frequencies, and that the PLIP must match the 10AS for it to work.  The frequency is not shown on the outside of the PLIP (at least not on mine) but if you open it up you can see that there is a small metal canister (round on earlier version, square on later ones).  This is part of a Surface Acoustic Wave (SAW) oscillator circuit, and you can tell the frequency from the part number.  The round cans have part numbers 1239 for 315MHz. and 1207 for 433.92 MHz.  The only square can I have found is mine and it is part number 2704 and 315 MHz, as you might expect from the table above, but a SAW product search showed that a similar device for 433.92 MHz had part number R 2701.

I assume that you must have a 418 or 433.9 MHz system, and I think that you should open the new PLIP and check that it is 433.9 MHz – and it is the same frequency as your old one.  If you get past that stage your dealer should be able program it – but although I have heard of the Autologic system I have never used (or even seen) it in action.  But the procedure should be fairly simple - get them to go the “PLIP Programming (Learn) Mode” of the 10AS and then press the PLIP “repeatedly” until either the relay clicks or the LED flashes (it is meant to be the hazards but they are not connected on the Plus 8).

And if that does not work?  Then I would reset the 10AS (Set to default) and then set all the parameters as I have documented in the presentation that I will send you, and after that carry out a “GEMS Security Learn” procedure.  You might want to get a Rovacom with the GEMS and Lucas 10AS modules at some time.

But if you pursue the local garage option I would take your mobile phone and have a ride home available…. If you are going to get them to program the PLIP, I would get them to check the GEMS settings, the DTCs and the idle settings at the same time since it should not cost any more while they have it coupled up to TestBook, Rovacom or AutoLogic.

If you need a spare remote (called a PLIP by LR).  The remote can be obtained from Atlantic British (http://www.roverparts.com/), Part Number YWX101230G, Two Button Remote, Discovery I, for $104.95 (yes I know – ouch).  In the UK, Check with Rpi or Rimmer. Or, if you have a friendly LR dealer they can get a PLIP for you too, and can easily program your Lucas 10AS for the new PLIP, and they can probably get a key for you at the same time. There are also plenty of them on ebay.co.uk

Here is one that has been succesfully tried.
 

PLIP KEYS: THE ROVER MANUAL found by Lorne Goldman May 21, 2006

CLICK

IMMOBILIZER ISSUE
from the eMog Pub, July 31, 2008

GoMoG has run across a number of  4/4s with an immobilizer issues. The Ford Morgans from 1999 use a key that is a melange of efforts and designs from  4-5 companies; Ford, Land Rover, Valeo, Morgan and likely another aftermarket supplier.

The keys are made by Valeo to LR specs but the security system (immobilizer) is Ford, represented by a chip glued in position to the key. When the little  chip falls off, the key will not start your Morgan. If you find it, you can re-glue it on and all's well.

So point one is to check your keys and their chips. It would be wise to  carry a tube of instant glue and a spare key because the only instant solution
to a missing chip is another key or a long tow home.

If you have lost the chip or want a spare,  you have two options (or less outside the UK). You can contact the Factory. They will normally offer you or dealer a full new key ignition system (with new keys) This is very costly and a long install. However, the parts for the key only are MDE1986 (the key) and MDE1987 and you can have your dealer to sepcifically order these only. If this works, it is a convenient source but very expensive.

However, any decent locksmith can help you out. Once they know where the key comes from (above) , they can get a "blank" in no time for your existing keys. I have been told by a number of dealers that it is easy for a locksmith to work out how to attach the Ford chip (for a negligible cost).

To program the new key, take the master key and insert it three times into the ignition, then insert the newly made for Morgan key. This will transfer the programming from the master to the new key's chip.