The brave and lucky might find cepes (Boletus edulis) in British woods - big, dark-capped, with a spongy underside. They are also quite easy to find commercially, not fresh, but sliced and dried (maybe labelled porcini). And, unlike most mushrooms, they go quite well with a number of wines.
None of the common mushrooms on sale in British supermarkets is the thing to buy if you want to show a wine off at its best, especially a red wine. Mushrooms - even cepes - make most red wines taste far more bitterly tannic than they are. That may not matter if the mushrooms are a minor ingredient in a dish, but a heap of mushrooms will do your red wine no favours. Unoaked white wines don't clash, but most will taste too brightly fruity to be a real match for mushrooms, and too tangily acid, unless the dish has some added acidity such as lemon juice or cooking wine.
Common field mushrooms went positively well with no wines in my experiments. (The same goes for mushroom soup). Common mushrooms are particularly prone to emphasise tannin in red wines. So are oyster mushrooms (both grey and yellow varieties), sold now by many supermarkets. Shitake mushrooms, also commercially farmed in Britain, are another matter. Their strong garlic flavour goes wonderfully with the northern Italian white wine Lugana, and nearly as well with simple, dry German Riesling.
It is less easy to find fresh morels in Britain, but they are around at this time of year. Most wines swamp their delicate flavour, but very light, gentle, untannic Pinot Noir hits the spot. Chanterelles are yummier, and good with Chablis.
Cepes, however, chime in with a variety of red wine flavours, provided they are low in tannin. One flavour that goes especially well with cepes is the Tempranillo grape of Spain. Mature ones are best, labelled 'Reserva' or 'Gran Reserva', from Valdepenas, Navarro, Rioja or Ribera del Duero. Pinot Noir is just as good. Mature Cahors or claret, Merlot and Cabernet Sauvignon, Italian Ciro or Nebbiolo (if you can find mature, untannic ones) all go well with cepes, too. Only Chablis stars amongst whites, but the mushrooms will probably need a squirt of lemon juice to match its acidity.
Fungus-friendly wines... For a mature Tempranillo, try the complex 1985 Campillo Rioja Gran Reserva (pounds 9.95 Waitrose) - a wine to drink now rather than keep. The 1986 vintage, just arriving in some stores, is also delicious. The northern supermarket chain of Morrisons is often a good source of delicious old Romanian Pinot Noir. Try its lovely 1990 Romanian Pinot Noir Reserve (a real snip at pounds 3.45). 1995 Young Vatted Pinot Noir, Dealul Mare, Romania (pounds 2.89 Kwik Save) isn't mature, but it's light, soft and attractive. Gentle Merlots are easy to find. All the following are delicious, soft and fruity: 1995 La Langue Merlot, Delta Domaines, Vin de Pays d'Oc (pounds 3.99 Victoria Wine Cellars and shops), Chilean 1995 Merlot, Errazuriz Estate (pounds 4.99 Berkeley Wines and Wine Cellar), Hungarian 1994 Merlot River Route (pounds 3.79 Berkeley Wines and Wine Cellar), or the organic 1995 Domaine de Picheral Merlot, Vin de Pays d'Oc (pounds 3.99 Safeway). For Chablis, the simple 1994 Chablis - not the Petit Chablis - (pounds 7.99 Marks & Spencer) is good. Enotria Winecellars of London SWI8 have a superb, soft, but intense 1995 Lugana Vigna Brolettino (pounds 9.95), which has just arrived on the shelves, or the 1994 Devil's Root Riesling (pounds 3.69 Sainsbury's) from Germany is a good, cheaper option.