Your allowance is low, ie 1 x carton = 200 cigarettes / 50gs hand rolling / 1 x bottle of spirits. It's your choice if you want to abuse the system, if you get pulled in the UK, you will lose them or be offered to pay the duty.
Flying back to Manchester we have always seen the customs out in force with loads being pulled, not sure about other airports.
I will hold my hands up and say we bring back 'some extras' but not as much as the early years we have been.
As for Dabolim, we visit in March/April and the stocks are low so we always fill up in the resort and miss out the airport.
As for prices, last season most places were charging on average 1000rps (£12) for 200 cigs, at the airport they worked out at £7.
If you go via Bahrain, they are also cheap at £6 per carton.
Watch where you buy from - quite a few fakes about, Elephant shop and Debbies in Candolim are genuine. Also a decent one in Calangute near to the shop that sells original footie shirts (10 packs x 50gs of hand rolling was about £14).
Spirits - other than Honeybee, I don't think it's worth the hassle with extra weight to worry about, UK prices are not bad .
Don't know what you smoke but if it's anything like Sovereign/Mayfair etc., try a brand called Wins - £3.50 per carton
Spike.

At Heathrow in April i was stopped by customs. The customs guy just asked me a few questions and let me go. I wont tell you how many cartons of cigarettes i had in my case but there was a lot.
Oh Wins cigarettes are what we call "sweep ups" Blue packet.I bought back Wills ,they are small but i like that .

for info guy,s are u sure it,s 1x 50g tobbacco.in thaland it.s 1/2 kilo. 5x 50g.

Doesn't matter where you fly from ( as long as it's outside the EU) the duty free allowance is the same flying into the UK.
A bottle of Gilbeys Gin is £3- £3.50 in a shop in Goa. Very cheap compared to the UK and from what I can remember cheaper than Duty free too but if you have limited luggage allowance you can't bring much back even if you have the will to carry it.

Hope this site makes some sense to those who are unsure of your allowances.
http://customs.hmrc.gov.uk/channelsPortalWebApp/channelsPortalWebApp.portal?_nfpb=true&_pageLabel=pageTravel_ShowContent&id=HMCE_PROD_010220&propertyType=document

thanks for info spike,i thought tobbacco was 5x50g,cause when we came back from thailand i was stopped and had my case opened ,i had 1kg and they said it was double what i should have. i said 1/2 was hubbys,they said ok,didnt search hubby,s bags. {thank god}